matplotlibcpp.h

#pragma once

#include <vector>
#include <map>
#include <array>
#include <numeric>
#include <algorithm>
#include <stdexcept>
#include <iostream>
#include <cstdint> // <cstdint> requires c++11 support
#include <functional>

#include <Python.h>

#ifndef WITHOUT_NUMPY
#  define NPY_NO_DEPRECATED_API NPY_1_7_API_VERSION
#  include <numpy/arrayobject.h>

#  ifdef WITH_OPENCV
#    include <opencv2/opencv.hpp>
#  endif // WITH_OPENCV

/*
 * A bunch of constants were removed in OpenCV 4 in favour of enum classes, so
 * define the ones we need here.
 */
#  if CV_MAJOR_VERSION > 3
#    define CV_BGR2RGB cv::COLOR_BGR2RGB
#    define CV_BGRA2RGBA cv::COLOR_BGRA2RGBA
#  endif
#endif // WITHOUT_NUMPY

#if PY_MAJOR_VERSION >= 3
#  define PyString_FromString PyUnicode_FromString
#  define PyInt_FromLong PyLong_FromLong
#  define PyString_FromString PyUnicode_FromString
#endif


namespace matplotlibcpp {
namespace detail {

static std::string s_backend;

struct _interpreter {
    PyObject *s_python_function_show;
    PyObject *s_python_function_close;
    PyObject *s_python_function_draw;
    PyObject *s_python_function_pause;
    PyObject *s_python_function_save;
    PyObject *s_python_function_figure;
    PyObject *s_python_function_fignum_exists;
    PyObject *s_python_function_plot;
    PyObject *s_python_function_quiver;
    PyObject *s_python_function_semilogx;
    PyObject *s_python_function_semilogy;
    PyObject *s_python_function_loglog;
    PyObject *s_python_function_fill;
    PyObject *s_python_function_fill_between;
    PyObject *s_python_function_hist;
    PyObject *s_python_function_imshow;
    PyObject *s_python_function_scatter;
    PyObject *s_python_function_boxplot;
    PyObject *s_python_function_subplot;
    PyObject *s_python_function_subplot2grid;
    PyObject *s_python_function_legend;
    PyObject *s_python_function_xlim;
    PyObject *s_python_function_ion;
    PyObject *s_python_function_ginput;
    PyObject *s_python_function_ylim;
    PyObject *s_python_function_title;
    PyObject *s_python_function_axis;
    PyObject *s_python_function_axvline;
    PyObject *s_python_function_xlabel;
    PyObject *s_python_function_ylabel;
    PyObject *s_python_function_gca;
    PyObject *s_python_function_xticks;
    PyObject *s_python_function_yticks;
    PyObject *s_python_function_tick_params;
    PyObject *s_python_function_grid;
    PyObject *s_python_function_clf;
    PyObject *s_python_function_errorbar;
    PyObject *s_python_function_annotate;
    PyObject *s_python_function_tight_layout;
    PyObject *s_python_colormap;
    PyObject *s_python_empty_tuple;
    PyObject *s_python_function_stem;
    PyObject *s_python_function_xkcd;
    PyObject *s_python_function_text;
    PyObject *s_python_function_suptitle;
    PyObject *s_python_function_bar;
    PyObject *s_python_function_colorbar;
    PyObject *s_python_function_subplots_adjust;


    /* For now, _interpreter is implemented as a singleton since its currently not possible to have
       multiple independent embedded python interpreters without patching the python source code
       or starting a separate process for each.
        http://bytes.com/topic/python/answers/793370-multiple-independent-python-interpreters-c-c-program
       */

    static _interpreter& get() {
        static _interpreter ctx;
        return ctx;
    }

    PyObject* safe_import(PyObject* module, std::string fname) {
        PyObject* fn = PyObject_GetAttrString(module, fname.c_str());

        if (!fn)
            throw std::runtime_error(std::string("Couldn't find required function: ") + fname);

        if (!PyFunction_Check(fn))
            throw std::runtime_error(fname + std::string(" is unexpectedly not a PyFunction."));

        return fn;
    }

private:

#ifndef WITHOUT_NUMPY
#  if PY_MAJOR_VERSION >= 3

    void *import_numpy() {
        import_array(); // initialize C-API
        return NULL;
    }

#  else

    void import_numpy() {
        import_array(); // initialize C-API
    }

#  endif
#endif

    _interpreter() {

        // optional but recommended
#if PY_MAJOR_VERSION >= 3
        wchar_t name[] = L"plotting";
#else
        char name[] = "plotting";
#endif
        Py_SetProgramName(name);
        Py_Initialize();

#ifndef WITHOUT_NUMPY
        import_numpy(); // initialize numpy C-API
#endif

        PyObject* matplotlibname = PyString_FromString("matplotlib");
        PyObject* pyplotname = PyString_FromString("matplotlib.pyplot");
        PyObject* cmname  = PyString_FromString("matplotlib.cm");
        PyObject* pylabname  = PyString_FromString("pylab");
        if (!pyplotname || !pylabname || !matplotlibname || !cmname) {
            throw std::runtime_error("couldnt create string");
        }

        PyObject* matplotlib = PyImport_Import(matplotlibname);
        Py_DECREF(matplotlibname);
        if (!matplotlib) {
            PyErr_Print();
            throw std::runtime_error("Error loading module matplotlib!");
        }

        // matplotlib.use() must be called *before* pylab, matplotlib.pyplot,
        // or matplotlib.backends is imported for the first time
        if (!s_backend.empty()) {
            PyObject_CallMethod(matplotlib, const_cast<char*>("use"), const_cast<char*>("s"), s_backend.c_str());
        }

        PyObject* pymod = PyImport_Import(pyplotname);
        Py_DECREF(pyplotname);
        if (!pymod) { throw std::runtime_error("Error loading module matplotlib.pyplot!"); }

        s_python_colormap = PyImport_Import(cmname);
        Py_DECREF(cmname);
        if (!s_python_colormap) { throw std::runtime_error("Error loading module matplotlib.cm!"); }

        PyObject* pylabmod = PyImport_Import(pylabname);
        Py_DECREF(pylabname);
        if (!pylabmod) { throw std::runtime_error("Error loading module pylab!"); }

        s_python_function_show = safe_import(pymod, "show");
        s_python_function_close = safe_import(pymod, "close");
        s_python_function_draw = safe_import(pymod, "draw");
        s_python_function_pause = safe_import(pymod, "pause");
        s_python_function_figure = safe_import(pymod, "figure");
        s_python_function_fignum_exists = safe_import(pymod, "fignum_exists");
        s_python_function_plot = safe_import(pymod, "plot");
        s_python_function_quiver = safe_import(pymod, "quiver");
        s_python_function_semilogx = safe_import(pymod, "semilogx");
        s_python_function_semilogy = safe_import(pymod, "semilogy");
        s_python_function_loglog = safe_import(pymod, "loglog");
        s_python_function_fill = safe_import(pymod, "fill");
        s_python_function_fill_between = safe_import(pymod, "fill_between");
        s_python_function_hist = safe_import(pymod,"hist");
        s_python_function_scatter = safe_import(pymod,"scatter");
        s_python_function_boxplot = safe_import(pymod,"boxplot");
        s_python_function_subplot = safe_import(pymod, "subplot");
        s_python_function_subplot2grid = safe_import(pymod, "subplot2grid");
        s_python_function_legend = safe_import(pymod, "legend");
        s_python_function_ylim = safe_import(pymod, "ylim");
        s_python_function_title = safe_import(pymod, "title");
        s_python_function_axis = safe_import(pymod, "axis");
        s_python_function_axvline = safe_import(pymod, "axvline");
        s_python_function_xlabel = safe_import(pymod, "xlabel");
        s_python_function_ylabel = safe_import(pymod, "ylabel");
        s_python_function_gca = safe_import(pymod, "gca");
        s_python_function_xticks = safe_import(pymod, "xticks");
        s_python_function_yticks = safe_import(pymod, "yticks");
        s_python_function_tick_params = safe_import(pymod, "tick_params");
        s_python_function_grid = safe_import(pymod, "grid");
        s_python_function_xlim = safe_import(pymod, "xlim");
        s_python_function_ion = safe_import(pymod, "ion");
        s_python_function_ginput = safe_import(pymod, "ginput");
        s_python_function_save = safe_import(pylabmod, "savefig");
        s_python_function_annotate = safe_import(pymod,"annotate");
        s_python_function_clf = safe_import(pymod, "clf");
        s_python_function_errorbar = safe_import(pymod, "errorbar");
        s_python_function_tight_layout = safe_import(pymod, "tight_layout");
        s_python_function_stem = safe_import(pymod, "stem");
        s_python_function_xkcd = safe_import(pymod, "xkcd");
        s_python_function_text = safe_import(pymod, "text");
        s_python_function_suptitle = safe_import(pymod, "suptitle");
        s_python_function_bar = safe_import(pymod,"bar");
        s_python_function_colorbar = PyObject_GetAttrString(pymod, "colorbar");
        s_python_function_subplots_adjust = safe_import(pymod,"subplots_adjust");
#ifndef WITHOUT_NUMPY
        s_python_function_imshow = safe_import(pymod, "imshow");
#endif
        s_python_empty_tuple = PyTuple_New(0);
    }

    ~_interpreter() {
        Py_Finalize();
    }
};

} // end namespace detail

    struct SettingValue {
        int type;
        bool boolValue;
        std::string stringValue;
        float floatValue;
        int intValue;

    public:
        static const int String = 0;
        static const int Bool = 1;
        static const int Float = 2;
        static const int Int = 3;

        SettingValue(const bool value) {
            this->boolValue = value;
            this->type = SettingValue::Bool;
        }

        SettingValue(std::string value) {
            this->stringValue = value;
            this->type = SettingValue::String;
        }

        SettingValue(float value) {
            this->floatValue = value;
            this->type = SettingValue::Float;
        }

        SettingValue(int value) {
            this->intValue = value;
            this->type = SettingValue::Int;
        }
    };

/// Select the backend
///
/// **NOTE:** This must be called before the first plot command to have
/// any effect.
///
/// Mainly useful to select the non-interactive 'Agg' backend when running
/// matplotlibcpp in headless mode, for example on a machine with no display.
///
/// See also: https://matplotlib.org/2.0.2/api/matplotlib_configuration_api.html#matplotlib.use
inline void backend(const std::string& name)
{
    detail::s_backend = name;
}

inline bool annotate(std::string annotation, double x, double y)
{
    PyObject * xy = PyTuple_New(2);
    PyObject * str = PyString_FromString(annotation.c_str());

    PyTuple_SetItem(xy,0,PyFloat_FromDouble(x));
    PyTuple_SetItem(xy,1,PyFloat_FromDouble(y));

    PyObject* kwargs = PyDict_New();
    PyDict_SetItemString(kwargs, "xy", xy);

    PyObject* args = PyTuple_New(1);
    PyTuple_SetItem(args, 0, str);

    PyObject* res = PyObject_Call(detail::_interpreter::get().s_python_function_annotate, args, kwargs);

    Py_DECREF(args);
    Py_DECREF(kwargs);

    if(res) Py_DECREF(res);

    return res;
}

namespace detail {

#ifndef WITHOUT_NUMPY
// Type selector for numpy array conversion
template <typename T> struct select_npy_type { const static NPY_TYPES type = NPY_NOTYPE; }; //Default
template <> struct select_npy_type<double> { const static NPY_TYPES type = NPY_DOUBLE; };
template <> struct select_npy_type<float> { const static NPY_TYPES type = NPY_FLOAT; };
template <> struct select_npy_type<bool> { const static NPY_TYPES type = NPY_BOOL; };
template <> struct select_npy_type<int8_t> { const static NPY_TYPES type = NPY_INT8; };
template <> struct select_npy_type<int16_t> { const static NPY_TYPES type = NPY_SHORT; };
template <> struct select_npy_type<int32_t> { const static NPY_TYPES type = NPY_INT; };
template <> struct select_npy_type<int64_t> { const static NPY_TYPES type = NPY_INT64; };
template <> struct select_npy_type<uint8_t> { const static NPY_TYPES type = NPY_UINT8; };
template <> struct select_npy_type<uint16_t> { const static NPY_TYPES type = NPY_USHORT; };
template <> struct select_npy_type<uint32_t> { const static NPY_TYPES type = NPY_ULONG; };
template <> struct select_npy_type<uint64_t> { const static NPY_TYPES type = NPY_UINT64; };

// Sanity checks; comment them out or change the numpy type below if you're compiling on
// a platform where they don't apply
static_assert(sizeof(long long) == 8);
template <> struct select_npy_type<long long> { const static NPY_TYPES type = NPY_INT64; };
static_assert(sizeof(unsigned long long) == 8);
template <> struct select_npy_type<unsigned long long> { const static NPY_TYPES type = NPY_UINT64; };
// TODO: add int, long, etc.

template<typename Numeric>
PyObject* get_array(const std::vector<Numeric>& v)
{
    detail::_interpreter::get(); //interpreter needs to be initialized for the numpy commands to work
    npy_intp vsize = v.size();
    NPY_TYPES type = select_npy_type<Numeric>::type;
    if (type == NPY_NOTYPE) {
        size_t memsize = v.size()*sizeof(double);
        double* dp = static_cast<double*>(::malloc(memsize));
        for (size_t i=0; i<v.size(); ++i)
            dp[i] = v[i];
        PyObject* varray = PyArray_SimpleNewFromData(1, &vsize, NPY_DOUBLE, dp);
        PyArray_UpdateFlags(reinterpret_cast<PyArrayObject*>(varray), NPY_ARRAY_OWNDATA);
        return varray;
    }
    
    PyObject* varray = PyArray_SimpleNewFromData(1, &vsize, type, (void*)(v.data()));
    return varray;
}


template<typename Numeric>
PyObject* get_2darray(const std::vector<::std::vector<Numeric>>& v)
{
    detail::_interpreter::get();    //interpreter needs to be initialized for the numpy commands to work
    if (v.size() < 1) throw std::runtime_error("get_2d_array v too small");

    npy_intp vsize[2] = {static_cast<npy_intp>(v.size()),
                         static_cast<npy_intp>(v[0].size())};

    PyArrayObject *varray =
        (PyArrayObject *)PyArray_SimpleNew(2, vsize, NPY_DOUBLE);

    double *vd_begin = static_cast<double *>(PyArray_DATA(varray));

    for (const ::std::vector<Numeric> &v_row : v) {
      if (v_row.size() != static_cast<size_t>(vsize[1]))
        throw std::runtime_error("Missmatched array size");
      std::copy(v_row.begin(), v_row.end(), vd_begin);
      vd_begin += vsize[1];
    }

    return reinterpret_cast<PyObject *>(varray);
}

#else // fallback if we don't have numpy: copy every element of the given vector

template<typename Numeric>
PyObject* get_array(const std::vector<Numeric>& v)
{
    PyObject* list = PyList_New(v.size());
    for(size_t i = 0; i < v.size(); ++i) {
        PyList_SetItem(list, i, PyFloat_FromDouble(v.at(i)));
    }
    return list;
}

#endif // WITHOUT_NUMPY

// sometimes, for labels and such, we need string arrays
inline PyObject * get_array(const std::vector<std::string>& strings)
{
  PyObject* list = PyList_New(strings.size());
  for (std::size_t i = 0; i < strings.size(); ++i) {
    PyList_SetItem(list, i, PyString_FromString(strings[i].c_str()));
  }
  return list;
}

// not all matplotlib need 2d arrays, some prefer lists of lists
template<typename Numeric>
PyObject* get_listlist(const std::vector<std::vector<Numeric>>& ll)
{
  PyObject* listlist = PyList_New(ll.size());
  for (std::size_t i = 0; i < ll.size(); ++i) {
    PyList_SetItem(listlist, i, get_array(ll[i]));
  }
  return listlist;
}

} // namespace detail

/// Plot a line through the given x and y data points..
/// 
/// See: https://matplotlib.org/3.2.1/api/_as_gen/matplotlib.pyplot.plot.html
template<typename Numeric>
bool plot(const std::vector<Numeric> &x, const std::vector<Numeric> &y, const std::map<std::string, std::string>& keywords)
{
    assert(x.size() == y.size());

    // using numpy arrays
    PyObject* xarray = detail::get_array(x);
    PyObject* yarray = detail::get_array(y);

    // construct positional args
    PyObject* args = PyTuple_New(2);
    PyTuple_SetItem(args, 0, xarray);
    PyTuple_SetItem(args, 1, yarray);

    // construct keyword args
    PyObject* kwargs = PyDict_New();
    for(std::map<std::string, std::string>::const_iterator it = keywords.begin(); it != keywords.end(); ++it)
    {
        PyDict_SetItemString(kwargs, it->first.c_str(), PyString_FromString(it->second.c_str()));
    }

    PyObject* res = PyObject_Call(detail::_interpreter::get().s_python_function_plot, args, kwargs);

    Py_DECREF(args);
    Py_DECREF(kwargs);
    if(res) Py_DECREF(res);

    return res;
}

// TODO - it should be possible to make this work by implementing
// a non-numpy alternative for `detail::get_2darray()`.
#ifndef WITHOUT_NUMPY
template <typename Numeric>
void plot_surface(const std::vector<::std::vector<Numeric>> &x,
                  const std::vector<::std::vector<Numeric>> &y,
                  const std::vector<::std::vector<Numeric>> &z,
                  const std::map<std::string, SettingValue> &keywords =
                      std::map<std::string, SettingValue>())
{
  // We lazily load the modules here the first time this function is called
  // because I'm not sure that we can assume "matplotlib installed" implies
  // "mpl_toolkits installed" on all platforms, and we don't want to require
  // it for people who don't need 3d plots.
  static PyObject *mpl_toolkitsmod = nullptr, *axis3dmod = nullptr;
  if (!mpl_toolkitsmod) {
    detail::_interpreter::get();

    PyObject* mpl_toolkits = PyString_FromString("mpl_toolkits");
    PyObject* axis3d = PyString_FromString("mpl_toolkits.mplot3d");
    if (!mpl_toolkits || !axis3d) { throw std::runtime_error("couldnt create string"); }

    mpl_toolkitsmod = PyImport_Import(mpl_toolkits);
    Py_DECREF(mpl_toolkits);
    if (!mpl_toolkitsmod) { throw std::runtime_error("Error loading module mpl_toolkits!"); }

    axis3dmod = PyImport_Import(axis3d);
    Py_DECREF(axis3d);
    if (!axis3dmod) { throw std::runtime_error("Error loading module mpl_toolkits.mplot3d!"); }
  }

  assert(x.size() == y.size());
  assert(y.size() == z.size());

  // using numpy arrays
  PyObject *xarray = detail::get_2darray(x);
  PyObject *yarray = detail::get_2darray(y);
  PyObject *zarray = detail::get_2darray(z);

  // construct positional args
  PyObject *args = PyTuple_New(3);
  PyTuple_SetItem(args, 0, xarray);
  PyTuple_SetItem(args, 1, yarray);
  PyTuple_SetItem(args, 2, zarray);

  // Build up the kw args.
  PyObject *kwargs = PyDict_New();

  for (std::map<std::string, SettingValue>::const_iterator it = keywords.begin();
       it != keywords.end(); ++it) {
      PyObject *key = PyString_FromString(it->first.c_str());
      SettingValue value = it->second;

      switch (value.type) {
          case SettingValue::String:
              PyDict_SetItem(kwargs, key, PyString_FromString(value.stringValue.c_str()));
              break;
          case SettingValue::Float:
              PyDict_SetItem(kwargs, key, PyFloat_FromDouble(value.floatValue));
              break;
          case SettingValue::Int:
              PyDict_SetItem(kwargs, key, PyInt_FromLong(value.intValue));
              break;
          case SettingValue::Bool:
              PyDict_SetItem(kwargs, key, PyBool_FromLong(value.boolValue));
              break;
      }
  }


  PyObject *fig =
      PyObject_CallObject(detail::_interpreter::get().s_python_function_figure,
                          detail::_interpreter::get().s_python_empty_tuple);
  if (!fig) throw std::runtime_error("Call to figure() failed.");

  PyObject *gca_kwargs = PyDict_New();
  PyDict_SetItemString(gca_kwargs, "projection", PyString_FromString("3d"));

  PyObject *gca = PyObject_GetAttrString(fig, "gca");
  if (!gca) throw std::runtime_error("No gca");
  Py_INCREF(gca);
  PyObject *axis = PyObject_Call(
      gca, detail::_interpreter::get().s_python_empty_tuple, gca_kwargs);

  if (!axis) throw std::runtime_error("No axis");
  Py_INCREF(axis);

  Py_DECREF(gca);
  Py_DECREF(gca_kwargs);

  PyObject *plot_surface = PyObject_GetAttrString(axis, "plot_surface");
  if (!plot_surface) throw std::runtime_error("No surface");
  Py_INCREF(plot_surface);
  PyObject *res = PyObject_Call(plot_surface, args, kwargs);
  if (!res) throw std::runtime_error("failed surface");
  Py_DECREF(plot_surface);

  Py_DECREF(axis);
  Py_DECREF(args);
  Py_DECREF(kwargs);
  if (res) Py_DECREF(res);
}
#endif // WITHOUT_NUMPY

template <typename Numeric>
void plot3(const std::vector<Numeric> &x,
                  const std::vector<Numeric> &y,
                  const std::vector<Numeric> &z,
                  const std::map<std::string, std::string> &keywords =
                      std::map<std::string, std::string>())
{
  // Same as with plot_surface: We lazily load the modules here the first time 
  // this function is called because I'm not sure that we can assume "matplotlib 
  // installed" implies "mpl_toolkits installed" on all platforms, and we don't 
  // want to require it for people who don't need 3d plots.
  static PyObject *mpl_toolkitsmod = nullptr, *axis3dmod = nullptr;
  if (!mpl_toolkitsmod) {
    detail::_interpreter::get();

    PyObject* mpl_toolkits = PyString_FromString("mpl_toolkits");
    PyObject* axis3d = PyString_FromString("mpl_toolkits.mplot3d");
    if (!mpl_toolkits || !axis3d) { throw std::runtime_error("couldnt create string"); }

    mpl_toolkitsmod = PyImport_Import(mpl_toolkits);
    Py_DECREF(mpl_toolkits);
    if (!mpl_toolkitsmod) { throw std::runtime_error("Error loading module mpl_toolkits!"); }

    axis3dmod = PyImport_Import(axis3d);
    Py_DECREF(axis3d);
    if (!axis3dmod) { throw std::runtime_error("Error loading module mpl_toolkits.mplot3d!"); }
  }

  assert(x.size() == y.size());
  assert(y.size() == z.size());

  PyObject *xarray = detail::get_array(x);
  PyObject *yarray = detail::get_array(y);
  PyObject *zarray = detail::get_array(z);

  // construct positional args
  PyObject *args = PyTuple_New(3);
  PyTuple_SetItem(args, 0, xarray);
  PyTuple_SetItem(args, 1, yarray);
  PyTuple_SetItem(args, 2, zarray);

  // Build up the kw args.
  PyObject *kwargs = PyDict_New();

  for (std::map<std::string, std::string>::const_iterator it = keywords.begin();
       it != keywords.end(); ++it) {
    PyDict_SetItemString(kwargs, it->first.c_str(),
                         PyString_FromString(it->second.c_str()));
  }

  PyObject *fig =
      PyObject_CallObject(detail::_interpreter::get().s_python_function_figure,
                          detail::_interpreter::get().s_python_empty_tuple);
  if (!fig) throw std::runtime_error("Call to figure() failed.");

  PyObject *gca_kwargs = PyDict_New();
  PyDict_SetItemString(gca_kwargs, "projection", PyString_FromString("3d"));

  PyObject *gca = PyObject_GetAttrString(fig, "gca");
  if (!gca) throw std::runtime_error("No gca");
  Py_INCREF(gca);
  PyObject *axis = PyObject_Call(
      gca, detail::_interpreter::get().s_python_empty_tuple, gca_kwargs);

  if (!axis) throw std::runtime_error("No axis");
  Py_INCREF(axis);

  Py_DECREF(gca);
  Py_DECREF(gca_kwargs);

  PyObject *plot3 = PyObject_GetAttrString(axis, "plot");
  if (!plot3) throw std::runtime_error("No 3D line plot");
  Py_INCREF(plot3);
  PyObject *res = PyObject_Call(plot3, args, kwargs);
  if (!res) throw std::runtime_error("Failed 3D line plot");
  Py_DECREF(plot3);

  Py_DECREF(axis);
  Py_DECREF(args);
  Py_DECREF(kwargs);
  if (res) Py_DECREF(res);
}

template<typename Numeric>
bool stem(const std::vector<Numeric> &x, const std::vector<Numeric> &y, const std::map<std::string, std::string>& keywords)
{
    assert(x.size() == y.size());

    // using numpy arrays
    PyObject* xarray = detail::get_array(x);
    PyObject* yarray = detail::get_array(y);

    // construct positional args
    PyObject* args = PyTuple_New(2);
    PyTuple_SetItem(args, 0, xarray);
    PyTuple_SetItem(args, 1, yarray);

    // construct keyword args
    PyObject* kwargs = PyDict_New();
    for (std::map<std::string, std::string>::const_iterator it =
            keywords.begin(); it != keywords.end(); ++it) {
        PyDict_SetItemString(kwargs, it->first.c_str(),
                PyString_FromString(it->second.c_str()));
    }

    PyObject* res = PyObject_Call(
            detail::_interpreter::get().s_python_function_stem, args, kwargs);

    Py_DECREF(args);
    Py_DECREF(kwargs);
    if (res)
        Py_DECREF(res);

    return res;
}

template< typename Numeric >
bool fill(const std::vector<Numeric>& x, const std::vector<Numeric>& y, const std::map<std::string, std::string>& keywords)
{
    assert(x.size() == y.size());

    // using numpy arrays
    PyObject* xarray = detail::get_array(x);
    PyObject* yarray = detail::get_array(y);

    // construct positional args
    PyObject* args = PyTuple_New(2);
    PyTuple_SetItem(args, 0, xarray);
    PyTuple_SetItem(args, 1, yarray);

    // construct keyword args
    PyObject* kwargs = PyDict_New();
    for (auto it = keywords.begin(); it != keywords.end(); ++it) {
        PyDict_SetItemString(kwargs, it->first.c_str(), PyUnicode_FromString(it->second.c_str()));
    }

    PyObject* res = PyObject_Call(detail::_interpreter::get().s_python_function_fill, args, kwargs);

    Py_DECREF(args);
    Py_DECREF(kwargs);

    if (res) Py_DECREF(res);

    return res;
}

template< typename Numeric >
bool fill_between(const std::vector<Numeric>& x, const std::vector<Numeric>& y1, const std::vector<Numeric>& y2, const std::map<std::string, std::string>& keywords)
{
    assert(x.size() == y1.size());
    assert(x.size() == y2.size());

    // using numpy arrays
    PyObject* xarray = detail::get_array(x);
    PyObject* y1array = detail::get_array(y1);
    PyObject* y2array = detail::get_array(y2);

    // construct positional args
    PyObject* args = PyTuple_New(3);
    PyTuple_SetItem(args, 0, xarray);
    PyTuple_SetItem(args, 1, y1array);
    PyTuple_SetItem(args, 2, y2array);

    // construct keyword args
    PyObject* kwargs = PyDict_New();
    for(std::map<std::string, std::string>::const_iterator it = keywords.begin(); it != keywords.end(); ++it) {
        PyDict_SetItemString(kwargs, it->first.c_str(), PyUnicode_FromString(it->second.c_str()));
    }

    PyObject* res = PyObject_Call(detail::_interpreter::get().s_python_function_fill_between, args, kwargs);

    Py_DECREF(args);
    Py_DECREF(kwargs);
    if(res) Py_DECREF(res);

    return res;
}

template< typename Numeric>
bool hist(const std::vector<Numeric>& y, long bins=10,std::string color="b",
          double alpha=1.0, bool cumulative=false)
{

    PyObject* yarray = detail::get_array(y);

    PyObject* kwargs = PyDict_New();
    PyDict_SetItemString(kwargs, "bins", PyLong_FromLong(bins));
    PyDict_SetItemString(kwargs, "color", PyString_FromString(color.c_str()));
    PyDict_SetItemString(kwargs, "alpha", PyFloat_FromDouble(alpha));
    PyDict_SetItemString(kwargs, "cumulative", cumulative ? Py_True : Py_False);

    PyObject* plot_args = PyTuple_New(1);

    PyTuple_SetItem(plot_args, 0, yarray);


    PyObject* res = PyObject_Call(detail::_interpreter::get().s_python_function_hist, plot_args, kwargs);


    Py_DECREF(plot_args);
    Py_DECREF(kwargs);
    if(res) Py_DECREF(res);

    return res;
}

#ifndef WITHOUT_NUMPY
namespace detail {

inline void imshow(void *ptr, const NPY_TYPES type, const int rows, const int columns, const int colors, const std::map<std::string, std::string> &keywords, PyObject** out)
{
    assert(type == NPY_UINT8 || type == NPY_FLOAT);
    assert(colors == 1 || colors == 3 || colors == 4);

    detail::_interpreter::get();    //interpreter needs to be initialized for the numpy commands to work

    // construct args
    npy_intp dims[3] = { rows, columns, colors };
    PyObject *args = PyTuple_New(1);
    PyTuple_SetItem(args, 0, PyArray_SimpleNewFromData(colors == 1 ? 2 : 3, dims, type, ptr));

    // construct keyword args
    PyObject* kwargs = PyDict_New();
    for(std::map<std::string, std::string>::const_iterator it = keywords.begin(); it != keywords.end(); ++it)
    {
        PyDict_SetItemString(kwargs, it->first.c_str(), PyUnicode_FromString(it->second.c_str()));
    }

    PyObject *res = PyObject_Call(detail::_interpreter::get().s_python_function_imshow, args, kwargs);
    Py_DECREF(args);
    Py_DECREF(kwargs);
    if (!res)
        throw std::runtime_error("Call to imshow() failed");
    if (out)
        *out = res;
    else
        Py_DECREF(res);
}

} // namespace detail

inline void imshow(const unsigned char *ptr, const int rows, const int columns, const int colors, const std::map<std::string, std::string> &keywords = {}, PyObject** out = nullptr)
{
    detail::imshow((void *) ptr, NPY_UINT8, rows, columns, colors, keywords, out);
}

inline void imshow(const float *ptr, const int rows, const int columns, const int colors, const std::map<std::string, std::string> &keywords = {}, PyObject** out = nullptr)
{
    detail::imshow((void *) ptr, NPY_FLOAT, rows, columns, colors, keywords, out);
}

#ifdef WITH_OPENCV
void imshow(const cv::Mat &image, const std::map<std::string, std::string> &keywords = {})
{
    // Convert underlying type of matrix, if needed
    cv::Mat image2;
    NPY_TYPES npy_type = NPY_UINT8;
    switch (image.type() & CV_MAT_DEPTH_MASK) {
    case CV_8U:
        image2 = image;
        break;
    case CV_32F:
        image2 = image;
        npy_type = NPY_FLOAT;
        break;
    default:
        image.convertTo(image2, CV_MAKETYPE(CV_8U, image.channels()));
    }

    // If color image, convert from BGR to RGB
    switch (image2.channels()) {
    case 3:
        cv::cvtColor(image2, image2, CV_BGR2RGB);
        break;
    case 4:
        cv::cvtColor(image2, image2, CV_BGRA2RGBA);
    }

    detail::imshow(image2.data, npy_type, image2.rows, image2.cols, image2.channels(), keywords);
}
#endif // WITH_OPENCV
#endif // WITHOUT_NUMPY

template<typename NumericX, typename NumericY>
bool scatter(const std::vector<NumericX>& x,
             const std::vector<NumericY>& y,
             const double s=1.0, // The marker size in points**2
             const std::map<std::string, std::string> & keywords = {})
{
    assert(x.size() == y.size());

    PyObject* xarray = detail::get_array(x);
    PyObject* yarray = detail::get_array(y);

    PyObject* kwargs = PyDict_New();
    PyDict_SetItemString(kwargs, "s", PyLong_FromLong(s));
    for (const auto& it : keywords)
    {
        PyDict_SetItemString(kwargs, it.first.c_str(), PyString_FromString(it.second.c_str()));
    }

    PyObject* plot_args = PyTuple_New(2);
    PyTuple_SetItem(plot_args, 0, xarray);
    PyTuple_SetItem(plot_args, 1, yarray);

    PyObject* res = PyObject_Call(detail::_interpreter::get().s_python_function_scatter, plot_args, kwargs);

    Py_DECREF(plot_args);
    Py_DECREF(kwargs);
    if(res) Py_DECREF(res);

    return res;
}

template<typename Numeric>
bool boxplot(const std::vector<std::vector<Numeric>>& data,
             const std::vector<std::string>& labels = {},
             const std::map<std::string, std::string> & keywords = {})
{
    PyObject* listlist = detail::get_listlist(data);
    PyObject* args = PyTuple_New(1);
    PyTuple_SetItem(args, 0, listlist);

    PyObject* kwargs = PyDict_New();

    // kwargs needs the labels, if there are (the correct number of) labels
    if (!labels.empty() && labels.size() == data.size()) {
        PyDict_SetItemString(kwargs, "labels", detail::get_array(labels));
    }

    // take care of the remaining keywords
    for (const auto& it : keywords)
    {
        PyDict_SetItemString(kwargs, it.first.c_str(), PyString_FromString(it.second.c_str()));
    }

    PyObject* res = PyObject_Call(detail::_interpreter::get().s_python_function_boxplot, args, kwargs);

    Py_DECREF(args);
    Py_DECREF(kwargs);

    if(res) Py_DECREF(res);

    return res;
}

template<typename Numeric>
bool boxplot(const std::vector<Numeric>& data,
             const std::map<std::string, std::string> & keywords = {})
{
    PyObject* vector = detail::get_array(data);
    PyObject* args = PyTuple_New(1);
    PyTuple_SetItem(args, 0, vector);

    PyObject* kwargs = PyDict_New();
    for (const auto& it : keywords)
    {
        PyDict_SetItemString(kwargs, it.first.c_str(), PyString_FromString(it.second.c_str()));
    }

    PyObject* res = PyObject_Call(detail::_interpreter::get().s_python_function_boxplot, args, kwargs);

    Py_DECREF(args);
    Py_DECREF(kwargs);

    if(res) Py_DECREF(res);

    return res;
}

template <typename Numeric>
bool bar(const std::vector<Numeric> &               x,
         const std::vector<Numeric> &               y,
         std::string                                ec       = "black",
         std::string                                ls       = "-",
         double                                     lw       = 1.0,
         const std::map<std::string, std::string> & keywords = {}) {
  PyObject * xarray = detail::get_array(x);
  PyObject * yarray = detail::get_array(y);

  PyObject * kwargs = PyDict_New();

  PyDict_SetItemString(kwargs, "ec", PyString_FromString(ec.c_str()));
  PyDict_SetItemString(kwargs, "ls", PyString_FromString(ls.c_str()));
  PyDict_SetItemString(kwargs, "lw", PyFloat_FromDouble(lw));

  for (std::map<std::string, std::string>::const_iterator it =
         keywords.begin();
       it != keywords.end();
       ++it) {
    PyDict_SetItemString(
      kwargs, it->first.c_str(), PyUnicode_FromString(it->second.c_str()));
  }

  PyObject * plot_args = PyTuple_New(2);
  PyTuple_SetItem(plot_args, 0, xarray);
  PyTuple_SetItem(plot_args, 1, yarray);

  PyObject * res = PyObject_Call(
    detail::_interpreter::get().s_python_function_bar, plot_args, kwargs);

  Py_DECREF(plot_args);
  Py_DECREF(kwargs);
  if (res) Py_DECREF(res);

  return res;
}

template <typename Numeric>
bool bar(const std::vector<Numeric> &               y,
         std::string                                ec       = "black",
         std::string                                ls       = "-",
         double                                     lw       = 1.0,
         const std::map<std::string, std::string> & keywords = {}) {
  using T = typename std::remove_reference<decltype(y)>::type::value_type;

  std::vector<T> x;
  for (std::size_t i = 0; i < y.size(); i++) { x.push_back(i); }

  return bar(x, y, ec, ls, lw, keywords);
}

inline bool subplots_adjust(const std::map<std::string, double>& keywords = {})
{

    PyObject* kwargs = PyDict_New();
    for (std::map<std::string, double>::const_iterator it =
            keywords.begin(); it != keywords.end(); ++it) {
        PyDict_SetItemString(kwargs, it->first.c_str(),
                             PyFloat_FromDouble(it->second));
    }


    PyObject* plot_args = PyTuple_New(0);

    PyObject* res = PyObject_Call(detail::_interpreter::get().s_python_function_subplots_adjust, plot_args, kwargs);

    Py_DECREF(plot_args);
    Py_DECREF(kwargs);
    if(res) Py_DECREF(res);

    return res;
}

template< typename Numeric>
bool named_hist(std::string label,const std::vector<Numeric>& y, long bins=10, std::string color="b", double alpha=1.0)
{
    PyObject* yarray = detail::get_array(y);

    PyObject* kwargs = PyDict_New();
    PyDict_SetItemString(kwargs, "label", PyString_FromString(label.c_str()));
    PyDict_SetItemString(kwargs, "bins", PyLong_FromLong(bins));
    PyDict_SetItemString(kwargs, "color", PyString_FromString(color.c_str()));
    PyDict_SetItemString(kwargs, "alpha", PyFloat_FromDouble(alpha));


    PyObject* plot_args = PyTuple_New(1);
    PyTuple_SetItem(plot_args, 0, yarray);

    PyObject* res = PyObject_Call(detail::_interpreter::get().s_python_function_hist, plot_args, kwargs);

    Py_DECREF(plot_args);
    Py_DECREF(kwargs);
    if(res) Py_DECREF(res);

    return res;
}

template<typename NumericX, typename NumericY>
bool plot(const std::vector<NumericX>& x, const std::vector<NumericY>& y, const std::string& s = "")
{
    assert(x.size() == y.size());

    PyObject* xarray = detail::get_array(x);
    PyObject* yarray = detail::get_array(y);

    PyObject* pystring = PyString_FromString(s.c_str());

    PyObject* plot_args = PyTuple_New(3);
    PyTuple_SetItem(plot_args, 0, xarray);
    PyTuple_SetItem(plot_args, 1, yarray);
    PyTuple_SetItem(plot_args, 2, pystring);

    PyObject* res = PyObject_CallObject(detail::_interpreter::get().s_python_function_plot, plot_args);

    Py_DECREF(plot_args);
    if(res) Py_DECREF(res);

    return res;
}

template<typename NumericX, typename NumericY, typename NumericU, typename NumericW>
bool quiver(const std::vector<NumericX>& x, const std::vector<NumericY>& y, const std::vector<NumericU>& u, const std::vector<NumericW>& w, const std::map<std::string, std::string>& keywords = {})
{
    assert(x.size() == y.size() && x.size() == u.size() && u.size() == w.size());

    PyObject* xarray = detail::get_array(x);
    PyObject* yarray = detail::get_array(y);
    PyObject* uarray = detail::get_array(u);
    PyObject* warray = detail::get_array(w);

    PyObject* plot_args = PyTuple_New(4);
    PyTuple_SetItem(plot_args, 0, xarray);
    PyTuple_SetItem(plot_args, 1, yarray);
    PyTuple_SetItem(plot_args, 2, uarray);
    PyTuple_SetItem(plot_args, 3, warray);

    // construct keyword args
    PyObject* kwargs = PyDict_New();
    for(std::map<std::string, std::string>::const_iterator it = keywords.begin(); it != keywords.end(); ++it)
    {
        PyDict_SetItemString(kwargs, it->first.c_str(), PyUnicode_FromString(it->second.c_str()));
    }

    PyObject* res = PyObject_Call(
            detail::_interpreter::get().s_python_function_quiver, plot_args, kwargs);

    Py_DECREF(kwargs);
    Py_DECREF(plot_args);
    if (res)
        Py_DECREF(res);

    return res;
}

template<typename NumericX, typename NumericY>
bool stem(const std::vector<NumericX>& x, const std::vector<NumericY>& y, const std::string& s = "")
{
    assert(x.size() == y.size());

    PyObject* xarray = detail::get_array(x);
    PyObject* yarray = detail::get_array(y);

    PyObject* pystring = PyString_FromString(s.c_str());

    PyObject* plot_args = PyTuple_New(3);
    PyTuple_SetItem(plot_args, 0, xarray);
    PyTuple_SetItem(plot_args, 1, yarray);
    PyTuple_SetItem(plot_args, 2, pystring);

    PyObject* res = PyObject_CallObject(
            detail::_interpreter::get().s_python_function_stem, plot_args);

    Py_DECREF(plot_args);
    if (res)
        Py_DECREF(res);

    return res;
}

template<typename NumericX, typename NumericY>
bool semilogx(const std::vector<NumericX>& x, const std::vector<NumericY>& y, const std::string& s = "")
{
    assert(x.size() == y.size());

    PyObject* xarray = detail::get_array(x);
    PyObject* yarray = detail::get_array(y);

    PyObject* pystring = PyString_FromString(s.c_str());

    PyObject* plot_args = PyTuple_New(3);
    PyTuple_SetItem(plot_args, 0, xarray);
    PyTuple_SetItem(plot_args, 1, yarray);
    PyTuple_SetItem(plot_args, 2, pystring);

    PyObject* res = PyObject_CallObject(detail::_interpreter::get().s_python_function_semilogx, plot_args);

    Py_DECREF(plot_args);
    if(res) Py_DECREF(res);

    return res;
}

template<typename NumericX, typename NumericY>
bool semilogy(const std::vector<NumericX>& x, const std::vector<NumericY>& y, const std::string& s = "")
{
    assert(x.size() == y.size());

    PyObject* xarray = detail::get_array(x);
    PyObject* yarray = detail::get_array(y);

    PyObject* pystring = PyString_FromString(s.c_str());

    PyObject* plot_args = PyTuple_New(3);
    PyTuple_SetItem(plot_args, 0, xarray);
    PyTuple_SetItem(plot_args, 1, yarray);
    PyTuple_SetItem(plot_args, 2, pystring);

    PyObject* res = PyObject_CallObject(detail::_interpreter::get().s_python_function_semilogy, plot_args);

    Py_DECREF(plot_args);
    if(res) Py_DECREF(res);

    return res;
}

template<typename NumericX, typename NumericY>
bool loglog(const std::vector<NumericX>& x, const std::vector<NumericY>& y, const std::string& s = "")
{
    assert(x.size() == y.size());

    PyObject* xarray = detail::get_array(x);
    PyObject* yarray = detail::get_array(y);

    PyObject* pystring = PyString_FromString(s.c_str());

    PyObject* plot_args = PyTuple_New(3);
    PyTuple_SetItem(plot_args, 0, xarray);
    PyTuple_SetItem(plot_args, 1, yarray);
    PyTuple_SetItem(plot_args, 2, pystring);

    PyObject* res = PyObject_CallObject(detail::_interpreter::get().s_python_function_loglog, plot_args);

    Py_DECREF(plot_args);
    if(res) Py_DECREF(res);

    return res;
}

template<typename NumericX, typename NumericY>
bool errorbar(const std::vector<NumericX> &x, const std::vector<NumericY> &y, const std::vector<NumericX> &yerr, const std::map<std::string, std::string> &keywords = {})
{
    assert(x.size() == y.size());

    PyObject* xarray = detail::get_array(x);
    PyObject* yarray = detail::get_array(y);
    PyObject* yerrarray = detail::get_array(yerr);

    // construct keyword args
    PyObject* kwargs = PyDict_New();
    for(std::map<std::string, std::string>::const_iterator it = keywords.begin(); it != keywords.end(); ++it)
    {
        PyDict_SetItemString(kwargs, it->first.c_str(), PyString_FromString(it->second.c_str()));
    }

    PyDict_SetItemString(kwargs, "yerr", yerrarray);

    PyObject *plot_args = PyTuple_New(2);
    PyTuple_SetItem(plot_args, 0, xarray);
    PyTuple_SetItem(plot_args, 1, yarray);

    PyObject *res = PyObject_Call(detail::_interpreter::get().s_python_function_errorbar, plot_args, kwargs);

    Py_DECREF(kwargs);
    Py_DECREF(plot_args);

    if (res)
        Py_DECREF(res);
    else
        throw std::runtime_error("Call to errorbar() failed.");

    return res;
}

template<typename Numeric>
bool named_plot(const std::string& name, const std::vector<Numeric>& y, const std::string& format = "")
{
    PyObject* kwargs = PyDict_New();
    PyDict_SetItemString(kwargs, "label", PyString_FromString(name.c_str()));

    PyObject* yarray = detail::get_array(y);

    PyObject* pystring = PyString_FromString(format.c_str());

    PyObject* plot_args = PyTuple_New(2);

    PyTuple_SetItem(plot_args, 0, yarray);
    PyTuple_SetItem(plot_args, 1, pystring);

    PyObject* res = PyObject_Call(detail::_interpreter::get().s_python_function_plot, plot_args, kwargs);

    Py_DECREF(kwargs);
    Py_DECREF(plot_args);
    if (res) Py_DECREF(res);

    return res;
}

template<typename Numeric>
bool named_plot(const std::string& name, const std::vector<Numeric>& x, const std::vector<Numeric>& y, const std::string& format = "")
{
    PyObject* kwargs = PyDict_New();
    PyDict_SetItemString(kwargs, "label", PyString_FromString(name.c_str()));

    PyObject* xarray = detail::get_array(x);
    PyObject* yarray = detail::get_array(y);

    PyObject* pystring = PyString_FromString(format.c_str());

    PyObject* plot_args = PyTuple_New(3);
    PyTuple_SetItem(plot_args, 0, xarray);
    PyTuple_SetItem(plot_args, 1, yarray);
    PyTuple_SetItem(plot_args, 2, pystring);

    PyObject* res = PyObject_Call(detail::_interpreter::get().s_python_function_plot, plot_args, kwargs);

    Py_DECREF(kwargs);
    Py_DECREF(plot_args);
    if (res) Py_DECREF(res);

    return res;
}

template<typename Numeric>
bool named_semilogx(const std::string& name, const std::vector<Numeric>& x, const std::vector<Numeric>& y, const std::string& format = "")
{
    PyObject* kwargs = PyDict_New();
    PyDict_SetItemString(kwargs, "label", PyString_FromString(name.c_str()));

    PyObject* xarray = detail::get_array(x);
    PyObject* yarray = detail::get_array(y);

    PyObject* pystring = PyString_FromString(format.c_str());

    PyObject* plot_args = PyTuple_New(3);
    PyTuple_SetItem(plot_args, 0, xarray);
    PyTuple_SetItem(plot_args, 1, yarray);
    PyTuple_SetItem(plot_args, 2, pystring);

    PyObject* res = PyObject_Call(detail::_interpreter::get().s_python_function_semilogx, plot_args, kwargs);

    Py_DECREF(kwargs);
    Py_DECREF(plot_args);
    if (res) Py_DECREF(res);

    return res;
}

template<typename Numeric>
bool named_semilogy(const std::string& name, const std::vector<Numeric>& x, const std::vector<Numeric>& y, const std::string& format = "")
{
    PyObject* kwargs = PyDict_New();
    PyDict_SetItemString(kwargs, "label", PyString_FromString(name.c_str()));

    PyObject* xarray = detail::get_array(x);
    PyObject* yarray = detail::get_array(y);

    PyObject* pystring = PyString_FromString(format.c_str());

    PyObject* plot_args = PyTuple_New(3);
    PyTuple_SetItem(plot_args, 0, xarray);
    PyTuple_SetItem(plot_args, 1, yarray);
    PyTuple_SetItem(plot_args, 2, pystring);

    PyObject* res = PyObject_Call(detail::_interpreter::get().s_python_function_semilogy, plot_args, kwargs);

    Py_DECREF(kwargs);
    Py_DECREF(plot_args);
    if (res) Py_DECREF(res);

    return res;
}

template<typename Numeric>
bool named_loglog(const std::string& name, const std::vector<Numeric>& x, const std::vector<Numeric>& y, const std::string& format = "")
{
    PyObject* kwargs = PyDict_New();
    PyDict_SetItemString(kwargs, "label", PyString_FromString(name.c_str()));

    PyObject* xarray = detail::get_array(x);
    PyObject* yarray = detail::get_array(y);

    PyObject* pystring = PyString_FromString(format.c_str());

    PyObject* plot_args = PyTuple_New(3);
    PyTuple_SetItem(plot_args, 0, xarray);
    PyTuple_SetItem(plot_args, 1, yarray);
    PyTuple_SetItem(plot_args, 2, pystring);
    PyObject* res = PyObject_Call(detail::_interpreter::get().s_python_function_loglog, plot_args, kwargs);

    Py_DECREF(kwargs);
    Py_DECREF(plot_args);
    if (res) Py_DECREF(res);

    return res;
}

template<typename Numeric>
bool plot(const std::vector<Numeric>& y, const std::string& format = "")
{
    std::vector<Numeric> x(y.size());
    for(size_t i=0; i<x.size(); ++i) x.at(i) = i;
    return plot(x,y,format);
}

template<typename Numeric>
bool plot(const std::vector<Numeric>& y, const std::map<std::string, std::string>& keywords)
{
    std::vector<Numeric> x(y.size());
    for(size_t i=0; i<x.size(); ++i) x.at(i) = i;
    return plot(x,y,keywords);
}

template<typename Numeric>
bool stem(const std::vector<Numeric>& y, const std::string& format = "")
{
    std::vector<Numeric> x(y.size());
    for (size_t i = 0; i < x.size(); ++i) x.at(i) = i;
    return stem(x, y, format);
}

template<typename Numeric>
void text(Numeric x, Numeric y, const std::string& s = "")
{
    PyObject* args = PyTuple_New(3);
    PyTuple_SetItem(args, 0, PyFloat_FromDouble(x));
    PyTuple_SetItem(args, 1, PyFloat_FromDouble(y));
    PyTuple_SetItem(args, 2, PyString_FromString(s.c_str()));

    PyObject* res = PyObject_CallObject(detail::_interpreter::get().s_python_function_text, args);
    if(!res) throw std::runtime_error("Call to text() failed.");

    Py_DECREF(args);
    Py_DECREF(res);
}

inline void colorbar(PyObject* mappable = NULL, const std::map<std::string, float>& keywords = {})
{
    if (mappable == NULL)
        throw std::runtime_error("Must call colorbar with PyObject* returned from an image, contour, surface, etc.");
    PyObject* args = PyTuple_New(1);
    PyTuple_SetItem(args, 0, mappable);

    PyObject* kwargs = PyDict_New();
    for(std::map<std::string, float>::const_iterator it = keywords.begin(); it != keywords.end(); ++it)
    {
        PyDict_SetItemString(kwargs, it->first.c_str(), PyFloat_FromDouble(it->second));
    }

    PyObject* res = PyObject_Call(detail::_interpreter::get().s_python_function_colorbar, args, kwargs);
    if(!res) throw std::runtime_error("Call to colorbar() failed.");

    Py_DECREF(args);
    Py_DECREF(kwargs);
    Py_DECREF(res);
}


inline long figure(long number = -1)
{
    PyObject *res;
    if (number == -1)
        res = PyObject_CallObject(detail::_interpreter::get().s_python_function_figure, detail::_interpreter::get().s_python_empty_tuple);
    else {
        assert(number > 0);

        // Make sure interpreter is initialised
        detail::_interpreter::get();

        PyObject *args = PyTuple_New(1);
        PyTuple_SetItem(args, 0, PyLong_FromLong(number));
        res = PyObject_CallObject(detail::_interpreter::get().s_python_function_figure, args);
        Py_DECREF(args);
    }

    if(!res) throw std::runtime_error("Call to figure() failed.");

    PyObject* num = PyObject_GetAttrString(res, "number");
    if (!num) throw std::runtime_error("Could not get number attribute of figure object");
    const long figureNumber = PyLong_AsLong(num);

    Py_DECREF(num);
    Py_DECREF(res);

    return figureNumber;
}

inline bool fignum_exists(long number)
{
    // Make sure interpreter is initialised
    detail::_interpreter::get();

    PyObject *args = PyTuple_New(1);
    PyTuple_SetItem(args, 0, PyLong_FromLong(number));
    PyObject *res = PyObject_CallObject(detail::_interpreter::get().s_python_function_fignum_exists, args);
    if(!res) throw std::runtime_error("Call to fignum_exists() failed.");

    bool ret = PyObject_IsTrue(res);
    Py_DECREF(res);
    Py_DECREF(args);

    return ret;
}

inline void figure_size(size_t w, size_t h)
{
    // Make sure interpreter is initialised
    detail::_interpreter::get();

    const size_t dpi = 100;
    PyObject* size = PyTuple_New(2);
    PyTuple_SetItem(size, 0, PyFloat_FromDouble((double)w / dpi));
    PyTuple_SetItem(size, 1, PyFloat_FromDouble((double)h / dpi));

    PyObject* kwargs = PyDict_New();
    PyDict_SetItemString(kwargs, "figsize", size);
    PyDict_SetItemString(kwargs, "dpi", PyLong_FromSize_t(dpi));

    PyObject* res = PyObject_Call(detail::_interpreter::get().s_python_function_figure,
            detail::_interpreter::get().s_python_empty_tuple, kwargs);

    Py_DECREF(kwargs);

    if(!res) throw std::runtime_error("Call to figure_size() failed.");
    Py_DECREF(res);
}

inline void legend()
{
    PyObject* res = PyObject_CallObject(detail::_interpreter::get().s_python_function_legend, detail::_interpreter::get().s_python_empty_tuple);
    if(!res) throw std::runtime_error("Call to legend() failed.");

    Py_DECREF(res);
}

template<typename Numeric>
void ylim(Numeric left, Numeric right)
{
    PyObject* list = PyList_New(2);
    PyList_SetItem(list, 0, PyFloat_FromDouble(left));
    PyList_SetItem(list, 1, PyFloat_FromDouble(right));

    PyObject* args = PyTuple_New(1);
    PyTuple_SetItem(args, 0, list);

    PyObject* res = PyObject_CallObject(detail::_interpreter::get().s_python_function_ylim, args);
    if(!res) throw std::runtime_error("Call to ylim() failed.");

    Py_DECREF(args);
    Py_DECREF(res);
}

template<typename Numeric>
void xlim(Numeric left, Numeric right)
{
    PyObject* list = PyList_New(2);
    PyList_SetItem(list, 0, PyFloat_FromDouble(left));
    PyList_SetItem(list, 1, PyFloat_FromDouble(right));

    PyObject* args = PyTuple_New(1);
    PyTuple_SetItem(args, 0, list);

    PyObject* res = PyObject_CallObject(detail::_interpreter::get().s_python_function_xlim, args);
    if(!res) throw std::runtime_error("Call to xlim() failed.");

    Py_DECREF(args);
    Py_DECREF(res);
}


inline double* xlim()
{
    PyObject* args = PyTuple_New(0);
    PyObject* res = PyObject_CallObject(detail::_interpreter::get().s_python_function_xlim, args);
    PyObject* left = PyTuple_GetItem(res,0);
    PyObject* right = PyTuple_GetItem(res,1);

    double* arr = new double[2];
    arr[0] = PyFloat_AsDouble(left);
    arr[1] = PyFloat_AsDouble(right);

    if(!res) throw std::runtime_error("Call to xlim() failed.");

    Py_DECREF(res);
    return arr;
}


inline double* ylim()
{
    PyObject* args = PyTuple_New(0);
    PyObject* res = PyObject_CallObject(detail::_interpreter::get().s_python_function_ylim, args);
    PyObject* left = PyTuple_GetItem(res,0);
    PyObject* right = PyTuple_GetItem(res,1);

    double* arr = new double[2];
    arr[0] = PyFloat_AsDouble(left);
    arr[1] = PyFloat_AsDouble(right);

    if(!res) throw std::runtime_error("Call to ylim() failed.");

    Py_DECREF(res);
    return arr;
}

template<typename Numeric>
inline void xticks(const std::vector<Numeric> &ticks, const std::vector<std::string> &labels = {}, const std::map<std::string, std::string>& keywords = {})
{
    assert(labels.size() == 0 || ticks.size() == labels.size());

    // using numpy array
    PyObject* ticksarray = detail::get_array(ticks);

    PyObject* args;
    if(labels.size() == 0) {
        // construct positional args
        args = PyTuple_New(1);
        PyTuple_SetItem(args, 0, ticksarray);
    } else {
        // make tuple of tick labels
        PyObject* labelstuple = PyTuple_New(labels.size());
        for (size_t i = 0; i < labels.size(); i++)
            PyTuple_SetItem(labelstuple, i, PyUnicode_FromString(labels[i].c_str()));

        // construct positional args
        args = PyTuple_New(2);
        PyTuple_SetItem(args, 0, ticksarray);
        PyTuple_SetItem(args, 1, labelstuple);
    }

    // construct keyword args
    PyObject* kwargs = PyDict_New();
    for(std::map<std::string, std::string>::const_iterator it = keywords.begin(); it != keywords.end(); ++it)
    {
        PyDict_SetItemString(kwargs, it->first.c_str(), PyString_FromString(it->second.c_str()));
    }

    PyObject* res = PyObject_Call(detail::_interpreter::get().s_python_function_xticks, args, kwargs);

    Py_DECREF(args);
    Py_DECREF(kwargs);
    if(!res) throw std::runtime_error("Call to xticks() failed");

    Py_DECREF(res);
}

template<typename Numeric>
inline void xticks(const std::vector<Numeric> &ticks, const std::map<std::string, std::string>& keywords)
{
    xticks(ticks, {}, keywords);
}

template<typename Numeric>
inline void yticks(const std::vector<Numeric> &ticks, const std::vector<std::string> &labels = {}, const std::map<std::string, std::string>& keywords = {})
{
    assert(labels.size() == 0 || ticks.size() == labels.size());

    // using numpy array
    PyObject* ticksarray = detail::get_array(ticks);

    PyObject* args;
    if(labels.size() == 0) {
        // construct positional args
        args = PyTuple_New(1);
        PyTuple_SetItem(args, 0, ticksarray);
    } else {
        // make tuple of tick labels
        PyObject* labelstuple = PyTuple_New(labels.size());
        for (size_t i = 0; i < labels.size(); i++)
            PyTuple_SetItem(labelstuple, i, PyUnicode_FromString(labels[i].c_str()));

        // construct positional args
        args = PyTuple_New(2);
        PyTuple_SetItem(args, 0, ticksarray);
        PyTuple_SetItem(args, 1, labelstuple);
    }

    // construct keyword args
    PyObject* kwargs = PyDict_New();
    for(std::map<std::string, std::string>::const_iterator it = keywords.begin(); it != keywords.end(); ++it)
    {
        PyDict_SetItemString(kwargs, it->first.c_str(), PyString_FromString(it->second.c_str()));
    }

    PyObject* res = PyObject_Call(detail::_interpreter::get().s_python_function_yticks, args, kwargs);

    Py_DECREF(args);
    Py_DECREF(kwargs);
    if(!res) throw std::runtime_error("Call to yticks() failed");

    Py_DECREF(res);
}

template<typename Numeric>
inline void yticks(const std::vector<Numeric> &ticks, const std::map<std::string, std::string>& keywords)
{
    yticks(ticks, {}, keywords);
}

inline void tick_params(const std::map<std::string, std::string>& keywords, const std::string axis = "both")
{
  // construct positional args
  PyObject* args;
  args = PyTuple_New(1);
  PyTuple_SetItem(args, 0, PyString_FromString(axis.c_str()));

  // construct keyword args
  PyObject* kwargs = PyDict_New();
  for (std::map<std::string, std::string>::const_iterator it = keywords.begin(); it != keywords.end(); ++it)
  {
    PyDict_SetItemString(kwargs, it->first.c_str(), PyString_FromString(it->second.c_str()));
  }


  PyObject* res = PyObject_Call(detail::_interpreter::get().s_python_function_tick_params, args, kwargs);

  Py_DECREF(args);
  Py_DECREF(kwargs);
  if (!res) throw std::runtime_error("Call to tick_params() failed");

  Py_DECREF(res);
}

inline void subplot(long nrows, long ncols, long plot_number)
{
    // Make sure interpreter is initialized
    detail::_interpreter::get();
    
    // construct positional args
    PyObject* args = PyTuple_New(3);
    PyTuple_SetItem(args, 0, PyFloat_FromDouble(nrows));
    PyTuple_SetItem(args, 1, PyFloat_FromDouble(ncols));
    PyTuple_SetItem(args, 2, PyFloat_FromDouble(plot_number));

    PyObject* res = PyObject_CallObject(detail::_interpreter::get().s_python_function_subplot, args);
    if(!res) throw std::runtime_error("Call to subplot() failed.");

    Py_DECREF(args);
    Py_DECREF(res);
}

inline void subplot2grid(long nrows, long ncols, long rowid=0, long colid=0, long rowspan=1, long colspan=1)
{
    PyObject* shape = PyTuple_New(2);
    PyTuple_SetItem(shape, 0, PyLong_FromLong(nrows));
    PyTuple_SetItem(shape, 1, PyLong_FromLong(ncols));

    PyObject* loc = PyTuple_New(2);
    PyTuple_SetItem(loc, 0, PyLong_FromLong(rowid));
    PyTuple_SetItem(loc, 1, PyLong_FromLong(colid));

    PyObject* args = PyTuple_New(4);
    PyTuple_SetItem(args, 0, shape);
    PyTuple_SetItem(args, 1, loc);
    PyTuple_SetItem(args, 2, PyLong_FromLong(rowspan));
    PyTuple_SetItem(args, 3, PyLong_FromLong(colspan));

    PyObject* res = PyObject_CallObject(detail::_interpreter::get().s_python_function_subplot2grid, args);
    if(!res) throw std::runtime_error("Call to subplot2grid() failed.");

    Py_DECREF(shape);
    Py_DECREF(loc);
    Py_DECREF(args);
    Py_DECREF(res);
}

inline void title(const std::string &titlestr, const std::map<std::string, std::string> &keywords = {})
{
    PyObject* pytitlestr = PyString_FromString(titlestr.c_str());
    PyObject* args = PyTuple_New(1);
    PyTuple_SetItem(args, 0, pytitlestr);

    PyObject* kwargs = PyDict_New();
    for (auto it = keywords.begin(); it != keywords.end(); ++it) {
        PyDict_SetItemString(kwargs, it->first.c_str(), PyUnicode_FromString(it->second.c_str()));
    }

    PyObject* res = PyObject_Call(detail::_interpreter::get().s_python_function_title, args, kwargs);
    if(!res) throw std::runtime_error("Call to title() failed.");

    Py_DECREF(args);
    Py_DECREF(kwargs);
    Py_DECREF(res);
}

inline void suptitle(const std::string &suptitlestr, const std::map<std::string, std::string> &keywords = {})
{
    // Make sure interpreter is initialized
    detail::_interpreter::get();
    
    PyObject* pysuptitlestr = PyString_FromString(suptitlestr.c_str());
    PyObject* args = PyTuple_New(1);
    PyTuple_SetItem(args, 0, pysuptitlestr);

    PyObject* kwargs = PyDict_New();
    for (auto it = keywords.begin(); it != keywords.end(); ++it) {
        PyDict_SetItemString(kwargs, it->first.c_str(), PyUnicode_FromString(it->second.c_str()));
    }

    PyObject* res = PyObject_Call(detail::_interpreter::get().s_python_function_suptitle, args, kwargs);
    if(!res) throw std::runtime_error("Call to suptitle() failed.");

    Py_DECREF(args);
    Py_DECREF(kwargs);
    Py_DECREF(res);
}

inline void axis(const std::string &axisstr)
{
    PyObject* str = PyString_FromString(axisstr.c_str());
    PyObject* args = PyTuple_New(1);
    PyTuple_SetItem(args, 0, str);

    PyObject* res = PyObject_CallObject(detail::_interpreter::get().s_python_function_axis, args);
    if(!res) throw std::runtime_error("Call to title() failed.");

    Py_DECREF(args);
    Py_DECREF(res);
}

inline void axvline(double x, double ymin = 0., double ymax = 1., const std::map<std::string, std::string>& keywords = std::map<std::string, std::string>())
{
    // construct positional args
    PyObject* args = PyTuple_New(3);
    PyTuple_SetItem(args, 0, PyFloat_FromDouble(x));
    PyTuple_SetItem(args, 1, PyFloat_FromDouble(ymin));
    PyTuple_SetItem(args, 2, PyFloat_FromDouble(ymax));

    // construct keyword args
    PyObject* kwargs = PyDict_New();
    for(std::map<std::string, std::string>::const_iterator it = keywords.begin(); it != keywords.end(); ++it)
    {
        PyDict_SetItemString(kwargs, it->first.c_str(), PyString_FromString(it->second.c_str()));
    }

    PyObject* res = PyObject_Call(detail::_interpreter::get().s_python_function_axvline, args, kwargs);

    Py_DECREF(args);
    Py_DECREF(kwargs);

    if(res) Py_DECREF(res);
}

inline void xlabel(const std::string &str, const std::map<std::string, std::string> &keywords = {})
{
    PyObject* pystr = PyString_FromString(str.c_str());
    PyObject* args = PyTuple_New(1);
    PyTuple_SetItem(args, 0, pystr);

    PyObject* kwargs = PyDict_New();
    for (auto it = keywords.begin(); it != keywords.end(); ++it) {
        PyDict_SetItemString(kwargs, it->first.c_str(), PyUnicode_FromString(it->second.c_str()));
    }

    PyObject* res = PyObject_Call(detail::_interpreter::get().s_python_function_xlabel, args, kwargs);
    if(!res) throw std::runtime_error("Call to xlabel() failed.");

    Py_DECREF(args);
    Py_DECREF(kwargs);
    Py_DECREF(res);
}

inline void ylabel(const std::string &str, const std::map<std::string, std::string>& keywords = {})
{
    PyObject* pystr = PyString_FromString(str.c_str());
    PyObject* args = PyTuple_New(1);
    PyTuple_SetItem(args, 0, pystr);

    PyObject* kwargs = PyDict_New();
    for (auto it = keywords.begin(); it != keywords.end(); ++it) {
        PyDict_SetItemString(kwargs, it->first.c_str(), PyUnicode_FromString(it->second.c_str()));
    }

    PyObject* res = PyObject_Call(detail::_interpreter::get().s_python_function_ylabel, args, kwargs);
    if(!res) throw std::runtime_error("Call to ylabel() failed.");

    Py_DECREF(args);
    Py_DECREF(kwargs);
    Py_DECREF(res);
}

inline void set_zlabel(const std::string &str, const std::map<std::string, std::string>& keywords = {}) {
    // Same as with plot_surface: We lazily load the modules here the first time 
    // this function is called because I'm not sure that we can assume "matplotlib 
    // installed" implies "mpl_toolkits installed" on all platforms, and we don't 
    // want to require it for people who don't need 3d plots.
    static PyObject *mpl_toolkitsmod = nullptr, *axis3dmod = nullptr;
    if (!mpl_toolkitsmod) {
        detail::_interpreter::get();

        PyObject* mpl_toolkits = PyString_FromString("mpl_toolkits");
        PyObject* axis3d = PyString_FromString("mpl_toolkits.mplot3d");
        if (!mpl_toolkits || !axis3d) { throw std::runtime_error("couldnt create string"); }

        mpl_toolkitsmod = PyImport_Import(mpl_toolkits);
        Py_DECREF(mpl_toolkits);
        if (!mpl_toolkitsmod) { throw std::runtime_error("Error loading module mpl_toolkits!"); }

        axis3dmod = PyImport_Import(axis3d);
        Py_DECREF(axis3d);
        if (!axis3dmod) { throw std::runtime_error("Error loading module mpl_toolkits.mplot3d!"); }
    }

    PyObject* pystr = PyString_FromString(str.c_str());
    PyObject* args = PyTuple_New(1);
    PyTuple_SetItem(args, 0, pystr);

    PyObject* kwargs = PyDict_New();
    for (auto it = keywords.begin(); it != keywords.end(); ++it) {
        PyDict_SetItemString(kwargs, it->first.c_str(), PyUnicode_FromString(it->second.c_str()));
    }

    PyObject *ax =
    PyObject_CallObject(detail::_interpreter::get().s_python_function_gca,
      detail::_interpreter::get().s_python_empty_tuple);
    if (!ax) throw std::runtime_error("Call to gca() failed.");
    Py_INCREF(ax);

    PyObject *zlabel = PyObject_GetAttrString(ax, "set_zlabel");
    if (!zlabel) throw std::runtime_error("Attribute set_zlabel not found.");
    Py_INCREF(zlabel);

    PyObject *res = PyObject_Call(zlabel, args, kwargs);
    if (!res) throw std::runtime_error("Call to set_zlabel() failed.");
    Py_DECREF(zlabel);

    Py_DECREF(ax);
    Py_DECREF(args);
    Py_DECREF(kwargs);
    if (res) Py_DECREF(res);
}

inline void grid(bool flag)
{
    PyObject* pyflag = flag ? Py_True : Py_False;
    Py_INCREF(pyflag);

    PyObject* args = PyTuple_New(1);
    PyTuple_SetItem(args, 0, pyflag);

    PyObject* res = PyObject_CallObject(detail::_interpreter::get().s_python_function_grid, args);
    if(!res) throw std::runtime_error("Call to grid() failed.");

    Py_DECREF(args);
    Py_DECREF(res);
}

inline void show(const bool block = true)
{
    PyObject* res;
    if(block)
    {
        res = PyObject_CallObject(
                detail::_interpreter::get().s_python_function_show,
                detail::_interpreter::get().s_python_empty_tuple);
    }
    else
    {
        PyObject *kwargs = PyDict_New();
        PyDict_SetItemString(kwargs, "block", Py_False);
        res = PyObject_Call( detail::_interpreter::get().s_python_function_show, detail::_interpreter::get().s_python_empty_tuple, kwargs);
       Py_DECREF(kwargs);
    }


    if (!res) throw std::runtime_error("Call to show() failed.");

    Py_DECREF(res);
}

inline void close()
{
    PyObject* res = PyObject_CallObject(
            detail::_interpreter::get().s_python_function_close,
            detail::_interpreter::get().s_python_empty_tuple);

    if (!res) throw std::runtime_error("Call to close() failed.");

    Py_DECREF(res);
}

inline void xkcd() {
    PyObject* res;
    PyObject *kwargs = PyDict_New();

    res = PyObject_Call(detail::_interpreter::get().s_python_function_xkcd,
            detail::_interpreter::get().s_python_empty_tuple, kwargs);

    Py_DECREF(kwargs);

    if (!res)
        throw std::runtime_error("Call to show() failed.");

    Py_DECREF(res);
}

inline void draw()
{
    PyObject* res = PyObject_CallObject(
        detail::_interpreter::get().s_python_function_draw,
        detail::_interpreter::get().s_python_empty_tuple);

    if (!res) throw std::runtime_error("Call to draw() failed.");

    Py_DECREF(res);
}

template<typename Numeric>
inline void pause(Numeric interval)
{
    PyObject* args = PyTuple_New(1);
    PyTuple_SetItem(args, 0, PyFloat_FromDouble(interval));

    PyObject* res = PyObject_CallObject(detail::_interpreter::get().s_python_function_pause, args);
    if(!res) throw std::runtime_error("Call to pause() failed.");

    Py_DECREF(args);
    Py_DECREF(res);
}

inline void save(const std::string& filename)
{
    PyObject* pyfilename = PyString_FromString(filename.c_str());

    PyObject* args = PyTuple_New(1);
    PyTuple_SetItem(args, 0, pyfilename);

    PyObject* res = PyObject_CallObject(detail::_interpreter::get().s_python_function_save, args);
    if (!res) throw std::runtime_error("Call to save() failed.");

    Py_DECREF(args);
    Py_DECREF(res);
}

inline void clf() {
    PyObject *res = PyObject_CallObject(
        detail::_interpreter::get().s_python_function_clf,
        detail::_interpreter::get().s_python_empty_tuple);

    if (!res) throw std::runtime_error("Call to clf() failed.");

    Py_DECREF(res);
}

    inline void ion() {
    PyObject *res = PyObject_CallObject(
        detail::_interpreter::get().s_python_function_ion,
        detail::_interpreter::get().s_python_empty_tuple);

    if (!res) throw std::runtime_error("Call to ion() failed.");

    Py_DECREF(res);
}

inline std::vector<std::array<double, 2>> ginput(const int numClicks = 1, const std::map<std::string, std::string>& keywords = {})
{
    PyObject *args = PyTuple_New(1);
    PyTuple_SetItem(args, 0, PyLong_FromLong(numClicks));

    // construct keyword args
    PyObject* kwargs = PyDict_New();
    for(std::map<std::string, std::string>::const_iterator it = keywords.begin(); it != keywords.end(); ++it)
    {
        PyDict_SetItemString(kwargs, it->first.c_str(), PyUnicode_FromString(it->second.c_str()));
    }

    PyObject* res = PyObject_Call(
        detail::_interpreter::get().s_python_function_ginput, args, kwargs);

    Py_DECREF(kwargs);
    Py_DECREF(args);
    if (!res) throw std::runtime_error("Call to ginput() failed.");

    const size_t len = PyList_Size(res);
    std::vector<std::array<double, 2>> out;
    out.reserve(len);
    for (size_t i = 0; i < len; i++) {
        PyObject *current = PyList_GetItem(res, i);
        std::array<double, 2> position;
        position[0] = PyFloat_AsDouble(PyTuple_GetItem(current, 0));
        position[1] = PyFloat_AsDouble(PyTuple_GetItem(current, 1));
        out.push_back(position);
    }
    Py_DECREF(res);

    return out;
}

// Actually, is there any reason not to call this automatically for every plot?
inline void tight_layout() {
    PyObject *res = PyObject_CallObject(
        detail::_interpreter::get().s_python_function_tight_layout,
        detail::_interpreter::get().s_python_empty_tuple);

    if (!res) throw std::runtime_error("Call to tight_layout() failed.");

    Py_DECREF(res);
}

// Support for variadic plot() and initializer lists:

namespace detail {

template<typename T>
using is_function = typename std::is_function<std::remove_pointer<std::remove_reference<T>>>::type;

template<bool obj, typename T>
struct is_callable_impl;

template<typename T>
struct is_callable_impl<false, T>
{
    typedef is_function<T> type;
}; // a non-object is callable iff it is a function

template<typename T>
struct is_callable_impl<true, T>
{
    struct Fallback { void operator()(); };
    struct Derived : T, Fallback { };

    template<typename U, U> struct Check;

    template<typename U>
    static std::true_type test( ... ); // use a variadic function to make sure (1) it accepts everything and (2) its always the worst match

    template<typename U>
    static std::false_type test( Check<void(Fallback::*)(), &U::operator()>* );

public:
    typedef decltype(test<Derived>(nullptr)) type;
    typedef decltype(&Fallback::operator()) dtype;
    static constexpr bool value = type::value;
}; // an object is callable iff it defines operator()

template<typename T>
struct is_callable
{
    // dispatch to is_callable_impl<true, T> or is_callable_impl<false, T> depending on whether T is of class type or not
    typedef typename is_callable_impl<std::is_class<T>::value, T>::type type;
};

template<typename IsYDataCallable>
struct plot_impl { };

template<>
struct plot_impl<std::false_type>
{
    template<typename IterableX, typename IterableY>
    bool operator()(const IterableX& x, const IterableY& y, const std::string& format)
    {
        // 2-phase lookup for distance, begin, end
        using std::distance;
        using std::begin;
        using std::end;

        auto xs = distance(begin(x), end(x));
        auto ys = distance(begin(y), end(y));
        assert(xs == ys && "x and y data must have the same number of elements!");

        PyObject* xlist = PyList_New(xs);
        PyObject* ylist = PyList_New(ys);
        PyObject* pystring = PyString_FromString(format.c_str());

        auto itx = begin(x), ity = begin(y);
        for(size_t i = 0; i < xs; ++i) {
            PyList_SetItem(xlist, i, PyFloat_FromDouble(*itx++));
            PyList_SetItem(ylist, i, PyFloat_FromDouble(*ity++));
        }

        PyObject* plot_args = PyTuple_New(3);
        PyTuple_SetItem(plot_args, 0, xlist);
        PyTuple_SetItem(plot_args, 1, ylist);
        PyTuple_SetItem(plot_args, 2, pystring);

        PyObject* res = PyObject_CallObject(detail::_interpreter::get().s_python_function_plot, plot_args);

        Py_DECREF(plot_args);
        if(res) Py_DECREF(res);

        return res;
    }
};

template<>
struct plot_impl<std::true_type>
{
    template<typename Iterable, typename Callable>
    bool operator()(const Iterable& ticks, const Callable& f, const std::string& format)
    {
        if(begin(ticks) == end(ticks)) return true;

        // We could use additional meta-programming to deduce the correct element type of y,
        // but all values have to be convertible to double anyways
        std::vector<double> y;
        for(auto x : ticks) y.push_back(f(x));
        return plot_impl<std::false_type>()(ticks,y,format);
    }
};

} // end namespace detail

// recursion stop for the above
template<typename... Args>
bool plot() { return true; }

template<typename A, typename B, typename... Args>
bool plot(const A& a, const B& b, const std::string& format, Args... args)
{
    return detail::plot_impl<typename detail::is_callable<B>::type>()(a,b,format) && plot(args...);
}

/*
 * This group of plot() functions is needed to support initializer lists, i.e. calling
 *    plot( {1,2,3,4} )
 */
inline bool plot(const std::vector<double>& x, const std::vector<double>& y, const std::string& format = "") {
    return plot<double,double>(x,y,format);
}

inline bool plot(const std::vector<double>& y, const std::string& format = "") {
    return plot<double>(y,format);
}

inline bool plot(const std::vector<double>& x, const std::vector<double>& y, const std::map<std::string, std::string>& keywords) {
    return plot<double>(x,y,keywords);
}

/*
 * This class allows dynamic plots, ie changing the plotted data without clearing and re-plotting
 */
class Plot
{
public:
    // default initialization with plot label, some data and format
    template<typename Numeric>
    Plot(const std::string& name, const std::vector<Numeric>& x, const std::vector<Numeric>& y, const std::string& format = "") {

        assert(x.size() == y.size());

        PyObject* kwargs = PyDict_New();
        if(name != "")
            PyDict_SetItemString(kwargs, "label", PyString_FromString(name.c_str()));

        PyObject* xarray = detail::get_array(x);
        PyObject* yarray = detail::get_array(y);

        PyObject* pystring = PyString_FromString(format.c_str());

        PyObject* plot_args = PyTuple_New(3);
        PyTuple_SetItem(plot_args, 0, xarray);
        PyTuple_SetItem(plot_args, 1, yarray);
        PyTuple_SetItem(plot_args, 2, pystring);

        PyObject* res = PyObject_Call(detail::_interpreter::get().s_python_function_plot, plot_args, kwargs);

        Py_DECREF(kwargs);
        Py_DECREF(plot_args);

        if(res)
        {
            line= PyList_GetItem(res, 0);

            if(line)
                set_data_fct = PyObject_GetAttrString(line,"set_data");
            else
                Py_DECREF(line);
            Py_DECREF(res);
        }
    }

    // shorter initialization with name or format only
    // basically calls line, = plot([], [])
    Plot(const std::string& name = "", const std::string& format = "")
        : Plot(name, std::vector<double>(), std::vector<double>(), format) {}

    template<typename Numeric>
    bool update(const std::vector<Numeric>& x, const std::vector<Numeric>& y) {
        assert(x.size() == y.size());
        if(set_data_fct)
        {
            PyObject* xarray = detail::get_array(x);
            PyObject* yarray = detail::get_array(y);

            PyObject* plot_args = PyTuple_New(2);
            PyTuple_SetItem(plot_args, 0, xarray);
            PyTuple_SetItem(plot_args, 1, yarray);

            PyObject* res = PyObject_CallObject(set_data_fct, plot_args);
            if (res) Py_DECREF(res);
            return res;
        }
        return false;
    }

    // clears the plot but keep it available
    bool clear() {
        return update(std::vector<double>(), std::vector<double>());
    }

    // definitely remove this line
    void remove() {
        if(line)
        {
            auto remove_fct = PyObject_GetAttrString(line,"remove");
            PyObject* args = PyTuple_New(0);
            PyObject* res = PyObject_CallObject(remove_fct, args);
            if (res) Py_DECREF(res);
        }
        decref();
    }

    ~Plot() {
        decref();
    }
private:

    void decref() {
        if(line)
            Py_DECREF(line);
        if(set_data_fct)
            Py_DECREF(set_data_fct);
    }


    PyObject* line = nullptr;
    PyObject* set_data_fct = nullptr;
};

} // end namespace matplotlibcpp