Fix mypy errors for arithmetic analysis algorithms (TheAlgorithms#4053)

Author: dhruvmanila

Diff for: arithmetic_analysis/in_static_equilibrium.py

@@ -1,19 +1,14 @@
 """
 Checks if a system of forces is in static equilibrium.
-
-python/black : true
-flake8 : passed
-mypy : passed
 """
+from typing import List
 
-from __future__ import annotations
-
-from numpy import array, cos, cross, radians, sin  # type: ignore
+from numpy import array, cos, cross, radians, sin
 
 
 def polar_force(
     magnitude: float, angle: float, radian_mode: bool = False
-) -> list[float]:
+) -> List[float]:
     """
     Resolves force along rectangular components.
     (force, angle) => (force_x, force_y)

Diff for: arithmetic_analysis/lu_decomposition.py

@@ -1,34 +1,64 @@
-"""Lower-Upper (LU) Decomposition."""
+"""Lower-Upper (LU) Decomposition.
 
-# lower–upper (LU) decomposition - https://en.wikipedia.org/wiki/LU_decomposition
-import numpy
+Reference:
+- https://en.wikipedia.org/wiki/LU_decomposition
+"""
+from typing import Tuple
 
+import numpy as np
+from numpy import ndarray
 
-def LUDecompose(table):
+
+def lower_upper_decomposition(table: ndarray) -> Tuple[ndarray, ndarray]:
+    """Lower-Upper (LU) Decomposition
+
+    Example:
+
+    >>> matrix = np.array([[2, -2, 1], [0, 1, 2], [5, 3, 1]])
+    >>> outcome = lower_upper_decomposition(matrix)
+    >>> outcome[0]
+    array([[1. , 0. , 0. ],
+           [0. , 1. , 0. ],
+           [2.5, 8. , 1. ]])
+    >>> outcome[1]
+    array([[  2. ,  -2. ,   1. ],
+           [  0. ,   1. ,   2. ],
+           [  0. ,   0. , -17.5]])
+
+    >>> matrix = np.array([[2, -2, 1], [0, 1, 2]])
+    >>> lower_upper_decomposition(matrix)
+    Traceback (most recent call last):
+    ...
+    ValueError: 'table' has to be of square shaped array but got a 2x3 array:
+    [[ 2 -2  1]
+     [ 0  1  2]]
+    """
     # Table that contains our data
     # Table has to be a square array so we need to check first
-    rows, columns = numpy.shape(table)
-    L = numpy.zeros((rows, columns))
-    U = numpy.zeros((rows, columns))
+    rows, columns = np.shape(table)
     if rows != columns:
-        return []
+        raise ValueError(
+            f"'table' has to be of square shaped array but got a {rows}x{columns} "
+            + f"array:\n{table}"
+        )
+    lower = np.zeros((rows, columns))
+    upper = np.zeros((rows, columns))
     for i in range(columns):
         for j in range(i):
-            sum = 0
+            total = 0
             for k in range(j):
-                sum += L[i][k] * U[k][j]
-            L[i][j] = (table[i][j] - sum) / U[j][j]
-        L[i][i] = 1
+                total += lower[i][k] * upper[k][j]
+            lower[i][j] = (table[i][j] - total) / upper[j][j]
+        lower[i][i] = 1
         for j in range(i, columns):
-            sum1 = 0
+            total = 0
             for k in range(i):
-                sum1 += L[i][k] * U[k][j]
-            U[i][j] = table[i][j] - sum1
-    return L, U
+                total += lower[i][k] * upper[k][j]
+            upper[i][j] = table[i][j] - total
+    return lower, upper
 
 
 if __name__ == "__main__":
-    matrix = numpy.array([[2, -2, 1], [0, 1, 2], [5, 3, 1]])
-    L, U = LUDecompose(matrix)
-    print(L)
-    print(U)
+    import doctest
+
+    doctest.testmod()

Diff for: arithmetic_analysis/newton_forward_interpolation.py

@@ -1,10 +1,11 @@
 # https://www.geeksforgeeks.org/newton-forward-backward-interpolation/
 
 import math
+from typing import List
 
 
 # for calculating u value
-def ucal(u, p):
+def ucal(u: float, p: int) -> float:
     """
     >>> ucal(1, 2)
     0
@@ -19,9 +20,9 @@ def ucal(u, p):
     return temp
 
 
-def main():
+def main() -> None:
     n = int(input("enter the numbers of values: "))
-    y = []
+    y: List[List[float]] = []
     for i in range(n):
         y.append([])
     for i in range(n):

Diff for: arithmetic_analysis/newton_raphson.py

@@ -4,11 +4,14 @@
 # quickly find a good approximation for the root of a real-valued function
 from decimal import Decimal
 from math import *  # noqa: F401, F403
+from typing import Union
 
 from sympy import diff
 
 
-def newton_raphson(func: str, a: int, precision: int = 10 ** -10) -> float:
+def newton_raphson(
+    func: str, a: Union[float, Decimal], precision: float = 10 ** -10
+) -> float:
     """Finds root from the point 'a' onwards by Newton-Raphson method
     >>> newton_raphson("sin(x)", 2)
     3.1415926536808043

Diff for: arithmetic_analysis/secant_method.py

@@ -1,28 +1,29 @@
-# Implementing Secant method in Python
-# Author: dimgrichr
-
-
-from math import exp
-
-
-def f(x):
-    """
-    >>> f(5)
-    39.98652410600183
-    """
-    return 8 * x - 2 * exp(-x)
-
-
-def SecantMethod(lower_bound, upper_bound, repeats):
-    """
-    >>> SecantMethod(1, 3, 2)
-    0.2139409276214589
-    """
-    x0 = lower_bound
-    x1 = upper_bound
-    for i in range(0, repeats):
-        x0, x1 = x1, x1 - (f(x1) * (x1 - x0)) / (f(x1) - f(x0))
-    return x1
-
-
-print(f"The solution is: {SecantMethod(1, 3, 2)}")
+"""
+Implementing Secant method in Python
+Author: dimgrichr
+"""
+from math import exp
+
+
+def f(x: float) -> float:
+    """
+    >>> f(5)
+    39.98652410600183
+    """
+    return 8 * x - 2 * exp(-x)
+
+
+def secant_method(lower_bound: float, upper_bound: float, repeats: int) -> float:
+    """
+    >>> secant_method(1, 3, 2)
+    0.2139409276214589
+    """
+    x0 = lower_bound
+    x1 = upper_bound
+    for i in range(0, repeats):
+        x0, x1 = x1, x1 - (f(x1) * (x1 - x0)) / (f(x1) - f(x0))
+    return x1
+
+
+if __name__ == "__main__":
+    print(f"Example: {secant_method(1, 3, 2) = }")