std::strtof, std::strtod, std::strtold

From Cppreference

Jump to: navigation, search
Defined in header <cstdlib>

float       strtof( const char *str, char **str_end );
(C++11 feature)
double      strtod( const char *str, char **str_end );

long double strtold( const char *str, char **str_end );
(C++11 feature)

Interprets a floating point value in a character string pointed to by str.

Function discards any whitespace characters 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 floating point value. The valid floating point value can be one of the following:

  • (optional) plus or minus sign
  • nonempty sequence of decimal digits optionally containing a decimal point character (defines significand)
  • (optional) e or E followed with optional minus or plus sign and nonempty sequence of decimal digits (defines exponent)
  • (optional) plus or minus sign
  • 0x or 0X
  • nonempty sequence of hexadecimal digits optionally containing a decimal point character (defines significand)
  • (optional) p or P followed with optional minus or plus sign and nonempty sequence of hexadecimal digits (defines exponent)
  • (optional) plus or minus sign
  • INF or INFINITY ignoring case
  • (optional) plus or minus sign
  • NAN or NAN(char_sequence) ignoring case of the NAN part. char_sequence can only contain alphanumeric characters. The result is a quiet NaN floating point value.

The functions sets the pointer pointed to by str_end to point to the character past the last character interpreted. If str_end is NULL, it is ignored.

Contents

[edit] Parameters

str - pointer to the null-terminated character string to be interpreted
str_end - pointer to a pointer to character.

[edit] Return value

floating point value corresponding to the contents of str on success. If the converted value falls out of range of corresponding return type, range error occurs and HUGE_VAL, HUGE_VALF or HUGE_VALL is returned. If no conversion can be performed, 0 is returned.

[edit] Example

[edit] See also

atof
converts a character string to a floating point value
(function)