C++ 在另一个函数中调用函数
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Calling functions within another function
提问by TThom246
I am writing a program. And in the main function "int main()" i call to a function called, lets say, "int X()". Inside "int X()" I would like to call to another function "void Y()". Any ideas how to do this? I tried, inside the X() function, doing "Y();" and "void Y();" but to no prevail. Any tips on getting this to work? if at all possible?
我正在写一个程序。在主函数“int main()”中，我调用了一个名为“int X()”的函数。在“int X()”中，我想调用另一个函数“void Y()”。任何想法如何做到这一点？我试过，在 X() 函数中，做 "Y();" 和“无效 Y();” 但以不占上风。有什么让这个工作的提示吗？如果可能？
ex.
前任。
#include<iostream>
int X()
{
Y();
}
void Y()
{
std::cout << "Hello";
}
int main()
{
X();
system("pause");
return 0;
}
回答by marcinj
You must declare Y() before using it:
你必须在使用它之前声明 Y() ：
void Y();
int X()
{Y();}
回答by Shoe
When the compiler reaches:
当编译器达到：
int X()
{
Y();
}
it doesn't know what Yis. You need to declare Ybefore Xby inverting their declarations:
它不知道是什么Y。需要声明Y之前X通过颠倒它们的声明：
void Y()
{
std::cout << "Hello";
}
int X()
{
Y();
}
int main()
{
X();
system("pause");
return 0;
}
You should also provide a return?value for X, otherwise a warning will pop up.
您还应该为 提供return? 值X，否则会弹出警告。
And please, don't follow the suggestion of using using namespace std;. The way you writing std::cout?is just fine.
并且请不要遵循使用using namespace std;. 你写的方式std::cout？很好。
And hereis the working example.
而这里是工作的例子。
回答by 3yakuya
You must define or declare your functions before you use them. For example:
在使用它们之前，您必须定义或声明您的函数。例如：
void Y(); //this is just a declaration, you need to implement this later in the code.
int X(){
//...
Y();
//...
return someIntValue; //you will get warned if function supposed to return something does not do it.
}
OR
或者
void Y(){
//code that Y is supposed to do...
}
int X(){
//...
Y();
//...
}
When you call the function you do not write its type anymore (to call functon Y you write: Y(arguments);and not void Y(arguments);). You write the type only when declaring or defining the function.
当你调用函数时，你不再写它的类型（调用函数 Y 你写：Y(arguments);而不是void Y(arguments);）。只有在声明或定义函数时才编写类型。
回答by user2345215
You need to declare the Yfunction before the Xfunction uses it.
您需要Y在X函数使用它之前声明该函数。
Write this line before the definition of X:
在定义之前写下这一行X：
void Y();
