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

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Defined in header <cstdlib>

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float       strtof( const char *str, char **str_end );

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double      strtod( const char *str, char **str_end );

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long double strtold( const char *str, char **str_end );

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Interprets an floating point value in a character 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 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.

(since C++11)

• any other expression that may be accepted by the currently installed C locale

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

Parameters

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

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, Template:cpp is returned.

See also

Template:cpp/string/narrow/dcl list atof