Conversions between various basic types of C + +

Common methods of conversion:

1. Circulation Exchange
2. function transformation in STL standard function library

Circulation Exchange

Stream conversion is mainly used in the <sstream> Library of the StringStream class.

The conversion between the basic types can be done through StringStream,

1#include <sstream>2 3 using namespacestd;4 5Template<typename Out_type, TypeName in_value>6 7Out_type CONVERT (ConstIn_value &t) {8 9 StringStream stream;Ten  OneStream <<T; A  - out_type result; -  theStream >>result; -  -     returnresult; -  +}

STL function Conversion

The standard function library contains functions for converting between basic types in the library <stdlib.h>.

Basic functions:

Itoa (): converts an integer value to a string.

Ltoa (): converts a long integer value to a string.

Ultoa (): converts an unsigned long integer value to a string.

GCVT (): converts a floating-point number to a string, rounded.

ECVT (): converts a double-precision floating-point value to a string that does not contain a decimal point in the conversion result.

FCVT (): Specifies the number of digits for the conversion precision, and the remainder with ECVT ().

Atof (): converts a string to a double-precision floating-point value.

Atoi (): converts a string to an integer value.

Atol (): converts a string to a long integer value.

Strtod (): converts a string to a double-precision floating-point value and reports all remaining digits that cannot be converted.

Strtol (): converts a string to a long integer value and reports all remaining digits that cannot be converted.

Strtoul (): converts a string to an unsigned long value and reports any remaining digits that cannot be converted.

Each function has different parameters, such as

char* itoa (int value, char* string, int radix)

Meaning: Converts an integer value into a string, radix to the base used for the conversion (the cardinality of the data saved to the string 2 8 10 16)

int atoi (const char* nptr)

Meaning: Skips the preceding space character until a number or sign is encountered to begin the conversion, and then ends the conversion with a non-numeric or string ending (' + ') and returns the result.

In this way, there is no flow conversion flexibility and convenience.

Instance:

(using stream conversion)

#include <iostream>#include<sstream>using namespacestd;template<typename Out_type, TypeName in_value>Out_type Convert (ConstIn_value &t)    {StringStream stream; Stream<<T;    Out_type result; Stream>>result; returnresult;}intMain () {Charxxx[Ten] ="45126"; inti =45641; I= convert<int>(XXX);//string converted to integer cout<<i;}

Results:

(using STL functions)

#include <iostream>#include<stdlib.h>using namespacestd;intMain () {inti =1254876; Charx[Ten]; Itoa (i, X,Ten); cout<< x <<Endl; intN; Char* y ="45128"; N=atoi (y); cout<< N <<Endl;}

Results:

Conversions between various basic types of C + +