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add replace_all documentation #3478

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Feb 25, 2019
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add replace_all documentation #3478

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6 changes: 5 additions & 1 deletion src/util/string_utils.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -162,17 +162,21 @@ std::string escape(const std::string &s)

/// Replace all occurrences of a string inside a string
/// \param [out] str: string to search
/// \param from: string to replace
/// \param from: string to replace; must be non-empty
/// \param to: string to replace with
/// Copyright notice:
/// Attributed to Gauthier Boaglio
/// Source: https://stackoverflow.com/a/24315631/7501486
/// Used under MIT license
/// Note that this is quadratic in str.size() if from.size() != to.size().
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... , because each replacement entails a copy of the contents of the string.

Or maybe something else?

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No, that would not change the complexity in str.size() -- unfortunately, std::string::replace does not provide the guarantee that replacing equal-length strings is not independent of the length of the containing string.

/// There is no guarantee that it is linear in str.size() if
/// from.size() == to.size().
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Why not?

void replace_all(
std::string &str,
const std::string &from,
const std::string &to)
{
PRECONDITION(!from.empty());
size_t start_pos = 0;
while((start_pos = str.find(from, start_pos)) != std::string::npos)
{
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