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Home » Tip Bank » C++
Language: C++
Expertise: Intermediate
Mar 19, 2001

Different Values For Default Arguments in Different Scopes


In the same scope, it’s not possible to have different values for default arguments. For example, this would be an error:
 
void foo(int i = 0){
    cout << i;
}
void foo(int = 1);//error

But default arguments can indeed take different values in different scopes. For example:
 
int Func(void){
    foo(int = 1);//ok, 1 will be used as the default value in the scope of
this function
}

To enforce this, a parameter must be supplied to the function. Declare the function without a default parameter:
 
int Func(void){
    foo(int);//disable the default parameter.
    foo(1);//ok.
    foo();//error, function foo() takes one parameter.
}

The opposite is also true--a function can be declared to take a default parameter even if it’s not defined that way.
 
void foo(int i){
	cout << i;
}

int Func(){
	void foo(int = 1);//enable default parameter
	foo();//ok.
}
Nitin Garg
 
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