Interprets a floating point value in a byte string pointed to bystr.

Function discards any whitespace characters (as determined bystd::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 Clocale) (defines significand)
• (optional)e orE followed with optional minus or plus sign and nonempty sequence of decimal digits (defines exponent to base10)

• any other expression that may be accepted by the currently installed Clocale.

The functions sets the pointer pointed to bystr_end to point to the character past the last character interpreted. Ifstr_end is a null pointer, it is ignored.

[edit]Parameters

[edit]Return value

Floating point value corresponding to the contents ofstr on success. If the converted value falls out of range of corresponding return type, range error occurs andHUGE_VAL,HUGE_VALF orHUGE_VALL is returned. If no conversion can be performed,​0​ is returned and*str_end is set tostr.

[edit]Example

#include <cerrno>#include <clocale>#include <cstdlib>#include <iostream>#include <string> int main(){constchar* p="111.11 -2.22 0X1.BC70A3D70A3D7P+6 -Inf 1.18973e+4932zzz";char* end{};std::cout<<"Parsing\""<< p<<"\":\n";errno=0;for(double f= std::strtod(p,&end); p!= end; f= std::strtod(p,&end)){std::cout<<"  '"<<std::string(p, end- p)<<"' -> ";        p= end;if(errno==ERANGE){std::cout<<"range error, got ";errno=0;}std::cout<< f<<'\n';} if(std::setlocale(LC_NUMERIC,"de_DE.utf8")){std::cout<<"With de_DE.utf8 locale:\n";std::cout<<"  '123.45' -> "<< std::strtod("123.45",0)<<'\n';std::cout<<"  '123,45' -> "<< std::strtod("123,45",0)<<'\n';}}

Parsing "111.11 -2.22 0X1.BC70A3D70A3D7P+6 -Inf 1.18973e+4932zzz":  '111.11' -> 111.11  ' -2.22' -> -2.22  ' 0X1.BC70A3D70A3D7P+6' -> 111.11  ' -Inf' -> -inf  ' 1.18973e+4932' -> range error, got infWith de_DE.utf8 locale:  '123.45' -> 123  '123,45' -> 123.45

[edit]See also

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