std::atof(3)

💖 NAME

Hey bestie! Welcome to std::atof(3) from the C++ Standard Libary 💖✨

std::atof — std::atof (the name is literally the name, periodt).

✨ Synopsis

          Defined in header <cstdlib>
          double atof( const char* str );

So std::atof interprets a floating point value in a byte string pointed to by str 🫶

It discards any whitespace characters (as determined by std::isspace) until the 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, bestie:

• decimal floating-point expression — it consists of these 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 these 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) (since C++11)
• infinity expression — it consists of these parts:
  • (optional) plus or minus sign
  • INF or INFINITY ignoring case
• not-a-number expression — it consists of these 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

🎀 Parameters

• str — pointer to the null-terminated byte string to be interpreted.

💫 Return value

A double value corresponding to the contents of str on success. If the converted value falls out of range of the return type, the return value is undefined 🚨. If no conversion can be performed, 0.0 is returned.

🧚 Example

// Run this code — yes bestie, run it, no cap:

       // Run this code

        #include <cstdlib>
        #include <iostream>

        int main()
        {
            std::cout << std::atof("0.0000000123") << '\n'
                      << std::atof("0.012") << '\n'
                      << std::atof("15e16") << '\n'
                      << std::atof("-0x1afp-2") << '\n'
                      << std::atof("inF") << '\n'
                      << std::atof("Nan") << '\n'
                      << std::atof("invalid") << '\n';
        }

🌈 Output

1.23e-08
0.012
1.5e+17
-107.75
inf
nan
0

🔥 See also

• stof, stod, stold — converts a string to a floating point value (function). Each one is marked (C++11).
• strtof, strtod, strtold — converts a byte string to a floating-point value (function).
• from_chars — converts a character sequence to an integer or floating-point value (function) (C++17).
• atoi, atol, atoll — converts a byte string to an integer value (function); atoll is marked (C++11).
• C documentation for atof.

okay that’s the whole page, bestie — source/version: http://cppreference.com, dated 2024.06.10 💅🫶