std::stof,s...,std::stold(3)

🌸 NAME 🌸

Bestie, this is the std::stof,std::stod,std::stold page — a.k.a. std::stof,s...,std::stold(3) — from the C++ Standard Libary. It's the slay little family that reads floating-point numbers out of strings ✨

✨ SYNOPSIS ✨

Defined in header <string> 🎀

• (1) (since C++11) — float stof ( const std::string& str, std::size_t* pos = nullptr );
• (2) (since C++11) — float stof ( const std::wstring& str, std::size_t* pos = nullptr );
• (3) (since C++11) — double stod ( const std::string& str, std::size_t* pos = nullptr );
• (4) (since C++11) — double stod ( const std::wstring& str, std::size_t* pos = nullptr );
• (5) (since C++11) — long double stold( const std::string& str, std::size_t* pos = nullptr );
• (6) (since C++11) — long double stold( const std::wstring& str, std::size_t* pos = nullptr );

Interprets a floating point value in a string str. No cap, that's literally the whole assignment 💅

Let ptr be an internal (to the conversion functions) pointer of type char* (1,3,5) or wchar_t* (2,4,6), accordingly.

1. Calls std::strtof(str.c_str(), &ptr).
2. Calls std::wcstof(str.c_str(), &ptr).
3. Calls std::strtod(str.c_str(), &ptr).
4. Calls std::wcstod(str.c_str(), &ptr).
5. Calls std::strtold(str.c_str(), &ptr).
6. Calls std::wcstold(str.c_str(), &ptr).

💫 the valid floating-point value menu 💫

Function discards any whitespace characters (as determined by std::isspace) until first non-whitespace character is found. Then it takes as many characters as possible to form a valid floating-point representation and converts them to a floating-point value. The valid floating-point value can be one of the following:

• decimal floating-point expression. It consists of the following parts:
  • (optional) plus or minus sign
  • nonempty sequence of decimal digits optionally containing decimal-point character (as determined by the current C locale) (defines significand)
  • (optional) e or E followed with optional minus or plus sign and nonempty sequence of decimal digits (defines exponent to base 10)
• hexadecimal floating-point expression. It consists of the following parts:
  • (optional) plus or minus sign
  • 0x or 0X
  • nonempty sequence of hexadecimal digits optionally containing a decimal-point character (as determined by the current C locale) (defines significand)
  • (optional) p or P followed with optional minus or plus sign and nonempty sequence of decimal digits (defines exponent to base 2)
• infinity expression. It consists of the following parts:
  • (optional) plus or minus sign
  • INF or INFINITY ignoring case
• not-a-number expression. It consists of the following parts:
  • (optional) plus or minus sign
  • NAN or NAN(char_sequence) ignoring case of the NAN part. char_sequence can only contain digits, Latin letters, and underscores. The result is a quiet NaN floating-point value.
• any other expression that may be accepted by the currently installed C locale

If pos is not a null pointer, then ptr will receive the address of the first unconverted character in str.c_str(), and the index of that character will be calculated and stored in *pos, giving the number of characters that were processed by the conversion. Tracked, bestie 🫶

💖 PARAMETERS 💖

• str — the string to convert.
• pos — address of an integer to store the number of characters processed.

🫶 RETURN VALUE 🫶

The string converted to the specified floating point type. That's the whole tea ☕

😭 EXCEPTIONS 😭

• std::invalid_argument if no conversion could be performed.
• std::out_of_range if the converted value would fall out of the range of the result type or if the underlying function (std::strtof, std::strtod or std::strtold) sets errno to ERANGE.

🦋 EXAMPLE 🦋

This section is incomplete 😭 Reason: no example.

🔥 DEFECT REPORTS 🔥

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

• DR LWG 2009 — applied to C++11. Behavior as published: std::out_of_range would not be thrown if the converted value would fall out of the range of the result type. Correct behavior: will throw.
• DR LWG 2403 — applied to C++11. Behavior as published: stof called std::strtod or std::wcstod. Correct behavior: stof calls std::strtof or std::wcstof.

🌈 SEE ALSO 🌈

• stoi (C++11), stol (C++11), stoll (C++11) — converts a string to a signed integer (function).
• stoul (C++11), stoull (C++11) — converts a string to an unsigned integer (function).
• from_chars (C++17) — converts a character sequence to an integer or floating-point value (function).

🎀 CATEGORY 🎀

• * Todo no example

Source/version: http://cppreference.com · date: 2024.06.10 — mwah, bestie 💋🫶