Embarassing, but necessary question

This is a discussion on Embarassing, but necessary question within the C Programming forums, part of the General Programming Boards category; Sorry, this is basic, so I refuse to not understand it: Code: main() { int number = 5; printf("%i devided ...

  1. #1
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    Embarassing, but necessary question

    Sorry, this is basic, so I refuse to not understand it:

    Code:
    main() {
    	int number = 5;
    	printf("%i devided by two is %d\n", tall, devider(tall));	
    
    }
    
    double devider(int x) {
    	return x/2;
    }
    This gives the warning:
    Code:
    test.c:7: warning: format ‘%d’ expects type ‘int’, but argument 3 has type ‘double’
    I don't understand this. I'm sending an in value to a function which returns a double. And the printf has %d for the returned double value.
    Still the compiler insists that %d expects an int variable?

    .

  2. #2
    &TH of undefined behavior Fordy's Avatar
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    %d isn't for double - printf - C++ Reference

  3. #3
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    Even more embarassing. Thanks :-)

  4. #4
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    You have a good compiler. What compiler is it?
    It's good habit to pay attention to compiler warnings.

  5. #5
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    where do you declare tall?


    His compiler is actually quite poor if that is the only warning he gets when he tried to compile that. He should get:

    Code:
    silly.c: In function ‘main’:
    silly.c:3: warning: incompatible implicit declaration of built-in function ‘printf’
    silly.c:3: error: ‘tall’ undeclared (first use in this function)
    silly.c:3: error: (Each undeclared identifier is reported only once
    silly.c:3: error: for each function it appears in.)
    silly.c: At top level:
    silly.c:7: error: conflicting types for ‘devider’
    silly.c:3: note: previous implicit declaration of ‘devider’ was here
    Even assuming he includes the necessary headers, it certainly should not compile without tall being declared.
    Last edited by KBriggs; 08-05-2010 at 10:18 AM.

  6. #6
    C++まいる!Cをこわせ!
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    Where is main's return type?
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

  7. #7
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    Indeed, %d is same as %i for integer integral values. Check your textbook to see what symbol you need to print a float or double value.

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