我如何重载功能 [英] How do I overload a function

问题描述

当我尝试...

void function(int y,int w)
{
    printf("int function");

}


void function(float y,float w)
{
   printf("float function");
}

 
int main()
{
   function(1.2,2.2);
   return 0;
}

我收到类似的错误错误.

I get an error error like..

error C2668: 'function' : ambiguous call to overloaded function

并且当我尝试调用function(1.2,2)或function(1,2.2)时，它正在打印为"int函数".

请澄清..何时函数(float y，float w)?

and when I''m trying to call function(1.2,2) or function(1,2.2) it is printing as "int function"

Please clarify..when will the function(float y,float w)?

推荐答案

除了Stuart所说的，如果您真的不想将函数签名从float更改为double，您始终可以使用键入为float的文字.如果将后缀f添加到浮点数，它们将被键入float.

In addition to what Stuart said, if you really don''t want to change the function signature from floatto double, you can always use literals that are typed as float. If you add the suffix f to the floating point numbers, they will be typed float.

您的示例将是function(1.2f, 2f)和function(1, 2.2f).

查看来自gcc的错误消息:

Look at the error message from gcc:

a.cpp:16: error: call of overloaded ‘function(double, double)’ is ambiguous
a.cpp:3: note: candidates are: void function(int, int)
a.cpp:9: note:                 void function(float, float)

调用这两个函数都需要截断，这就是为什么两个函数都不是另一个函数的原因.我怀疑您真的想要void function(double y,double w).请记住，在C/C ++中，用于文字和参数传递的默认浮点类型是double，而不是float.

A call to either function would require truncation, which is why neither is preferred over the other. I suspect you really want void function(double y,double w). Remember that in C/C++, the default floating-point type for literals and parameter passing is double, NOT float.

请想象一下如何传递参数.

如果将其作为1.2和2.2传递给(int，int)函数，则它将被截断为1和2.

如果将其作为1.2和2.2传递给(float，float)，则将按原样进行处理.

这就是歧义蔓延的地方.

我发现了两种解决此问题的方法.
首先是文字的使用:-

Just imagine how your arguments would be passed.

If it is passed as 1.2 and 2.2 to the (int,int) function then it would to truncated to 1 and 2.

If it is passed as 1.2 and 2.2 to the (float,float) it will be processed as is.

So here is where the ambiguity creeps in.

I have found two ways to solve this problem.
First is the use of literals:-

int main()
{
        function(1.2F,2.2F);
	return 0;
}

其次，按照我喜欢的方式，它始终有效(也可以用于C ++的默认转换和升级).
对于int:-

Secondly, and the way I like to do it, It always works (and can also be used for C++''s default conversion and promotion).
For int:-

int main()
{
int a=1.2, b=2.2;
	function(a,b);
	return 0;
}

对于浮动:-

For Float:-

int main()
{
float a=1.2, b=2.2;
	function(a,b);
	return 0;
}

因此，不要使用实际的DIGITS.最好先将它们声明为类型，然后再声明为重载！

现在看，如果以(1.2,2)或(1,2.2)的形式发送它，则编译器可以简单地将其发送到int函数，它将起作用.
但是，要将其发送到float函数，编译器必须将2提升为float.促销仅在找不到匹配项时发生.

参考:-
使用C ++的计算机科学
住田Arora
章:函数重载

So instead of using actual DIGITS. It is better to declare them as a type first, then overload!

See now, if you send it as (1.2,2) or (1,2.2) then compiler can simply send it to the int function and it would work.
However, to send it to the float function the compiler would have to promote 2 to float. Promotion only happens when no match is found.

Refer:-
Computer Science with C++
Sumita Arora
Chapter: Function Overloading

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