Optional Arguments

This is a discussion on Optional Arguments within the C++ Programming forums, part of the General Programming Boards category; Code: // Header file: void GetInput(string ErrMsg = ""); //Source file: void GetInput(string ErrMsg = "") { int iTempX = ...

  1. #1
    C++ Developer XSquared's Avatar
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    Optional Arguments

    Code:
    // Header file:
    void GetInput(string ErrMsg = "");
    
    //Source file:
    void GetInput(string ErrMsg = "")
    {
    	int iTempX = 0;
    	int iTempY = 0;
    
    	char cTempX = 'A';
    
    	cout<<"Please enter the x-coord: ";
    	cin>>cTempX;
    	
    	iTempX = cTempX - 'A';
    
    	cout<<"Please enter the y-coord: ";
    	cin>>iTempY;
    
    	iTempY--;	
    }
    I get the error "GetInput' : redefinition of default parameter : parameter 1".
    Naturally I didn't feel inspired enough to read all the links for you, since I already slaved away for long hours under a blistering sun pressing the search button after typing four whole words! - Quzah

    You. Fetch me my copy of the Wall Street Journal. You two, fight to the death - Stewie

  2. #2
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    If my memory serves me correctly (which it probably doesn't), then you can only initialise default parameters in the definition. Try losing the default parameter from the (C++) declaration.

  3. #3
    C++ Developer XSquared's Avatar
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    If I change the function prototype to 'void GetInput(string ErrMsg)', then when I call it using 'GetInput();', I get the following error message: 'error C2660: 'GetInput' : function does not take 0 parameters'
    Naturally I didn't feel inspired enough to read all the links for you, since I already slaved away for long hours under a blistering sun pressing the search button after typing four whole words! - Quzah

    You. Fetch me my copy of the Wall Street Journal. You two, fight to the death - Stewie

  4. #4
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    Then you haven't given it a default parameter.

    This works -

    Code:
    #include <iostream>
    
    using namespace std;
    
    // Header file:
    void GetInput(string ErrMsg);
    
    //Source file:
    void GetInput(string ErrMsg = "")
    {
    	int iTempX = 0;
    	int iTempY = 0;
    
    	char cTempX = 'A';
    
    	cout<<"Please enter the x-coord: ";
    	cin>>cTempX;
    	
    	iTempX = cTempX - 'A';
    
    	cout<<"Please enter the y-coord: ";
    	cin>>iTempY;
    
    	iTempY--;	
    }
    
    
    int main()
    {
    	GetInput();
    	return 0;
    }

  5. #5
    C++ Developer XSquared's Avatar
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    That works IF they are in the same file. But if the prototype is in "theheader.h", the code is in "theheader.cpp", and int main() is in "main.cpp", it doesn't work.
    Naturally I didn't feel inspired enough to read all the links for you, since I already slaved away for long hours under a blistering sun pressing the search button after typing four whole words! - Quzah

    You. Fetch me my copy of the Wall Street Journal. You two, fight to the death - Stewie

  6. #6
    erstwhile
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    Drop the default parameter in the source file fn definition - only have the default in the header file fn declaration.

    (BTW, given that it looks like you've tried just about every other permutation, I would imagine you've already arrived at this conclusion. ).

  7. #7
    C++ Developer XSquared's Avatar
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    Actually, I hadn't tried that.

    It works now. Thanks.
    Naturally I didn't feel inspired enough to read all the links for you, since I already slaved away for long hours under a blistering sun pressing the search button after typing four whole words! - Quzah

    You. Fetch me my copy of the Wall Street Journal. You two, fight to the death - Stewie

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