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std::atof(3) C++ Standard Libary std::atof(3) NAME std::atof - std::atof Synopsis Defined in header <cstdlib> double atof( const char* str ); Interprets a floating point value in a byte string pointed to by str. Function discards any whitespace characters (as determined by std::isspace) until first non-whitespace character is found. Then it takes as many char- acters 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 deci- mal-point character (as determined by the current C locale) (defines sig- nificand) * (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) (since C++11) * 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 in- stalled C locale Parameters str - pointer to the null-terminated byte string to be interpreted Return value 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 unde- fined. If no conversion can be performed, 0.0 is returned. Example // 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 (C++11) (function) (C++11) (C++11) strtof converts a byte string to a floating-point value strtod (function) strtold from_chars converts a character sequence to an integer or floating- point value (C++17) (function) atoi atol converts a byte string to an integer value atoll (function) (C++11) C documentation for atof http://cppreference.com 2024.06.10 std::atof(3)
NAME | Synopsis | Parameters | Return value | Example | Output: | See also
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