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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::is-
     space) until
	first non-whitespace character is found. Then it takes as  many  charac-
     ters 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	signifi-
     cand)
	  * (optional) e or E followed with optional minus or plus sign and non-
     empty
	    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 installed
     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 undefined. 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)
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