From Cppreference





double atof( const char *str );





Interprets an floating point value in a character string pointed to by str.
Function discards any whitespace characters until first nonwhitespace 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:
 decimal floating point expression. It consists of the following parts:
 (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)
 binary 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 (defines significand)
 (optional) p or P followed with optional minus or plus sign and nonempty sequence of hexadecimal digits (defines exponent)
 infinity expression. It consists of the following parts:
 (optional) plus or minus sign
 INF or INFINITY ignoring case
 notanumber 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 alphanumeric characters. The result is a quiet NaN floating point value.
[edit] Parameters
str



pointer to the nullterminated character string to be interpreted

[edit] Return value
double value corresponding to the contents of str on success. If the converted value falls out of range of corresponding return type, HUGE_VAL is returned. If no conversion can be performed, 0.0 is returned.
[edit] Example
[edit] See also


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