char_traits::compare

项目
07/29/2015

Compares up to a specified number of characters in two strings.

static int compare( 
   const char_type* _Str1,  
   const char_type* _Str2,  
   size_t _Num  
);

Parameters

_Str1
The first of two strings to be compared to each other.
_Str2
The second of two strings to be compared to each other.
_Num
The number of elements in the strings to be compared.

Return Value

A negative value if the first string is less than the second string, 0 if the two strings are equal, or a positive value if the first string is greater than the second string.

Remarks

The comparison between the strings is made element by element, first testing for equality and then, if a pair of elements in the sequence tests not equal, they are tested for less than.

If two strings compare equal over a range but one is longer than the other, then the shorter of the two is less than the longer one.

Example

// char_traits_compare.cpp
// compile with: /EHsc
#include <string>
#include <iostream>

int main() {
   using namespace std;

   char_traits<char>::char_type* s1 = "CAB";
   char_traits<char>::char_type* s2 = "ABC";
   char_traits<char>::char_type* s3 = "ABC";
   char_traits<char>::char_type* s4 = "ABCD";
   
   cout << "The string s1 is: " << s1 << endl;
   cout << "The string s2 is: " << s2 << endl;
   cout << "The string s3 is: " << s3 << endl;
   cout << "The string s4 is: " << s4 << endl;

   int comp1, comp2, comp3, comp4;
   comp1 = char_traits<char>::compare ( s1 , s2 , 2 );
   comp2 = char_traits<char>::compare ( s2 , s3 , 3 );
   comp3 = char_traits<char>::compare ( s3 , s4 , 4 );
   comp4 = char_traits<char>::compare ( s4 , s3 , 4 );
   cout << "compare ( s1 , s2 , 2 ) = " << comp1 << endl;
   cout << "compare ( s2 , s3 , 3 ) = " << comp2 << endl;
   cout << "compare ( s3 , s4 , 4 ) = " << comp3 << endl;
   cout << "compare ( s4 , s3 , 4 ) = " << comp4 << endl;
}

Sample Output

The string s1 is: CAB
The string s2 is: ABC
The string s3 is: ABC
The string s4 is: ABCD
compare ( s1 , s2 , 2 ) = 1
compare ( s2 , s3 , 3 ) = 0
compare ( s3 , s4 , 4 ) = -1
compare ( s4 , s3 , 4 ) = 1

Requirements

Header: <string>

Namespace: std

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