string::operator==
說明如何使用 string::operator = = STL Visual C++ 中的函式。
template<class _E, class _TYPE, class _A> inline
bool operator==(
const basic_string<_E, _TYPE, _A>& LString,
const _E *RCharArray
);
template<class _E, class _TYPE, class _A> inline
bool operator==(
const _E * LCharArray, const basic_string<_E, _TYPE, _A>& RString
);
template<class _E, class _TYPE, class _A> inline
bool operator==(
const basic_string<_E, _TYPE, _A>& LString,
const basic_string<_E, _TYPE, _A>& RString
);
備註
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在原型中的類別/參數名稱不相符的標頭檔中的版本。某些已修改以提高可讀性。 |
有三種版本的 string::operator = = 函式。 前兩個函式比較對 basic_string 的 null 結尾字元陣列。 它們執行這項作業使用的 basic_string string::compare 函式,並傳回 ,則為 true 如果比較函式會傳回 0 的值。 第三個函式會比較兩個 basic_string 變數,使用 string::compare 的第二個加入 basic_string 的函式。 如需有關比較 函式,請參閱 string::compare 函式。 請注意,此運算子不適用於 NULL 指標為字元陣列。 您必須確定的字元陣列不是 NULL 之前將它傳遞給操作員。
範例
// StringEqual.cpp
// compile with: /EHsc
// Illustrates how to use the operator== to test for
// equality of a basic_string variable and a
// null-terminated string. It also illustrates how to
// use the operator== to test for equality of two
// basic_string variables.
//
// Functions:
//
// operator== returns true if the basic_string and the null-
// terminated string are equal.
// operator== returns true if both basic_strings are equal.
//////////////////////////////////////////////////////////////////////
#pragma warning(disable:4786)
#include <string>
#include <iostream>
using namespace std ;
void trueFalse(int x)
{
cout << (x? "True": "False") << endl;
}
int main()
{
string S1="ABC";
string S2="ABC";
string S3="DEF";
string S4; //This specifies an empty initial-controlled sequence.
char CP1[]="abc";
char CP2[]="DEF";
char *CP3 = NULL;
cout << "S1 is " << S1 << endl;
cout << "S2 is " << S2 << endl;
cout << "S3 is " << S3 << endl;
cout << "S4 is" << S4 << endl;
cout << "CP1 is " << CP1 << endl;
cout << "CP2 is " << CP2 << endl;
cout << "S1==CP1 returned ";
trueFalse(S1==CP1); // False (calls function 1)
cout << "S1==CP2 returned ";
trueFalse(S1==CP2); // False (calls function 1)
cout << "CP1==S1 returned ";
trueFalse(CP1==S1); // False (calls function 2)
cout << "CP2==S1 returned ";
trueFalse(CP2==S1); // False (calls function 2)
cout << "S1==S2 returned ";
trueFalse(S1==S2); // True (calls function 3)
cout << "S1==S3 returned ";
trueFalse(S1==S3); // False (calls function 3)
cout << "S1==S4 returned ";
trueFalse(S1==S4); // False (calls function 3)
// Following use of the operator will cause the program to
// crash since CP3 is NULL.
// cout << "S1==CP3 returned ";
// trueFalse(S1==CP3);
}
需求
標頭: <string>