Defining functions outside main - problem

This is a discussion on Defining functions outside main - problem within the C++ Programming forums, part of the General Programming Boards category; I am trying to define a function outside main, and the function will be used inside a loop(think thats where ...

  1. #1
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    Defining functions outside main - problem

    I am trying to define a function outside main, and the function will be used inside a loop(think thats where my probelms lie), here are the relevant bits of code. would be grateful of any help you could give me some advice/help (NB: i have attached the full code):

    Code:
    float f1(float Co1[10], float x3[100], int i);
    
    int main ()
    
    (
    
    .....
    
    float Co[10]; float x[100]; int i;
    
    
    int result;
    
    for(i=0;i<15;i++)
    {
    result= f1(Co, x, i);
    
    coutf(x)= "<<result<<endl;
    
    if(fabs(f1(Co,x,i))<0.00000001)
    {
    cout<<"The value of f(x) at the root is: "<<result<<endl;
    cout<<endl;
    return(0);
    }
    }
    }
    
    
    float f1(float Co[10], float x[100], int i)
    {
    float result;
    result=((Co1[0]*x[i]*x[i])+(Co1[1]*x[i])+Co1[2]);
    return(result);
    }
    Last edited by helpmeout; 03-21-2006 at 05:48 PM.

  2. #2
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    NB: i have attached the full code
    Maybe that code will erase every file on my computer.

  3. #3
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    i didnt know you could do that with a cpp! erm, i have now written the vital bits of code in. sorry

  4. #4
    carry on JaWiB's Avatar
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    Umm, so what's the problem? It looks like you fixed the syntax error.
    "Think not but that I know these things; or think
    I know them not: not therefore am I short
    Of knowing what I ought."
    -John Milton, Paradise Regained (1671)

    "Work hard and it might happen."
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    it doesnt build, come up with a few errors, argument from int to float, assignment from int to float

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    redefintions of i and undeclared variables, sort those errors out.
    When no one helps you out. Call google();

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    redefinitions of i and undeclared variables......as in ive used i twice? dont really understand what your saying.

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    yes thats what it means. i run your prog on my machine and this is what it comes up with.
    ompiling...
    test3232.cpp
    D:\Program Files\Microsoft Visual Studio\MyProjects\test3232\test3232.cpp(7) : error C2143: syntax error : missing ')' before ';'
    D:\Program Files\Microsoft Visual Studio\MyProjects\test3232\test3232.cpp(7) : error C2091: function returns function
    D:\Program Files\Microsoft Visual Studio\MyProjects\test3232\test3232.cpp(12) : error C2143: syntax error : missing ';' before 'for'
    D:\Program Files\Microsoft Visual Studio\MyProjects\test3232\test3232.cpp(12) : error C2143: syntax error : missing ')' before ';'
    D:\Program Files\Microsoft Visual Studio\MyProjects\test3232\test3232.cpp(12) : error C2143: syntax error : missing ';' before '<'
    D:\Program Files\Microsoft Visual Studio\MyProjects\test3232\test3232.cpp(12) : error C2501: 'i' : missing storage-class or type specifiers
    D:\Program Files\Microsoft Visual Studio\MyProjects\test3232\test3232.cpp(12) : error C2086: 'i' : redefinition
    D:\Program Files\Microsoft Visual Studio\MyProjects\test3232\test3232.cpp(12) : error C2143: syntax error : missing ';' before '<'
    D:\Program Files\Microsoft Visual Studio\MyProjects\test3232\test3232.cpp(12) : error C2143: syntax error : missing ';' before '++'
    D:\Program Files\Microsoft Visual Studio\MyProjects\test3232\test3232.cpp(12) : error C2501: 'i' : missing storage-class or type specifiers
    D:\Program Files\Microsoft Visual Studio\MyProjects\test3232\test3232.cpp(12) : error C2086: 'i' : redefinition
    D:\Program Files\Microsoft Visual Studio\MyProjects\test3232\test3232.cpp(12) : error C2143: syntax error : missing ';' before '++'
    D:\Program Files\Microsoft Visual Studio\MyProjects\test3232\test3232.cpp(12) : error C2059: syntax error : ')'
    D:\Program Files\Microsoft Visual Studio\MyProjects\test3232\test3232.cpp(13) : error C2143: syntax error : missing ';' before '{'
    D:\Program Files\Microsoft Visual Studio\MyProjects\test3232\test3232.cpp(13) : error C2447: missing function header (old-style formal list?)
    D:\Program Files\Microsoft Visual Studio\MyProjects\test3232\test3232.cpp(16) : error C2001: newline in constant
    D:\Program Files\Microsoft Visual Studio\MyProjects\test3232\test3232.cpp(31) : error C2065: 'Co1' : undeclared identifier
    D:\Program Files\Microsoft Visual Studio\MyProjects\test3232\test3232.cpp(31) : error C2109: subscript requires array or pointer type
    D:\Program Files\Microsoft Visual Studio\MyProjects\test3232\test3232.cpp(31) : error C2109: subscript requires array or pointer type
    D:\Program Files\Microsoft Visual Studio\MyProjects\test3232\test3232.cpp(31) : error C2109: subscript requires array or pointer type
    Error executing cl.exe.

    test3232.obj - 20 error(s), 0 warning(s)
    When no one helps you out. Call google();

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    oh dear, i still dont understand what i have to change though! argh

  10. #10
    carry on JaWiB's Avatar
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    When I downloaded the attachment, I only received one error and one warning. The error was on the line:
    Code:
    if(fabs(f1(i))<E)
    //looks like it should be
    if(fabs(f1(Co, x, i))<E)
    And the warning is:
    "warning C4244: '=' : conversion from 'float' to 'int', possible loss of data"
    on this line:
    Code:
    result= f1(Co, x, i);
    "Think not but that I know these things; or think
    I know them not: not therefore am I short
    Of knowing what I ought."
    -John Milton, Paradise Regained (1671)

    "Work hard and it might happen."
    -XSquared

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    yeah, but what does that mean? does no-one here actually know what this is? or does everyone just copy it without understanding it???

  12. #12
    C++ Witch laserlight's Avatar
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    but what does that mean
    f1() takes a float as an argument, but you are trying to pass an int. It is possible to cast to float, but then f1() takes 3 arguments, and you only provide one, so the problem runs deeper than that.
    Quote Originally Posted by Bjarne Stroustrup (2000-10-14)
    I get maybe two dozen requests for help with some sort of programming or design problem every day. Most have more sense than to send me hundreds of lines of code. If they do, I ask them to find the smallest example that exhibits the problem and send me that. Mostly, they then find the error themselves. "Finding the smallest program that demonstrates the error" is a powerful debugging tool.
    Look up a C++ Reference and learn How To Ask Questions The Smart Way

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    ok, im starting to understand a bit more, my programme takes f1 to be float but wants to make it an int? how do i fix the problem? i've tried everything to try and get it to work and nothing is working!

  14. #14
    C++ Witch laserlight's Avatar
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    Before you start thinking about casting, examine:
    Code:
    float f1(float Co1[10], float x3[100], int i);
    and its use in:
    Code:
    f1(i)
    Can you see what's wrong?
    Quote Originally Posted by Bjarne Stroustrup (2000-10-14)
    I get maybe two dozen requests for help with some sort of programming or design problem every day. Most have more sense than to send me hundreds of lines of code. If they do, I ask them to find the smallest example that exhibits the problem and send me that. Mostly, they then find the error themselves. "Finding the smallest program that demonstrates the error" is a powerful debugging tool.
    Look up a C++ Reference and learn How To Ask Questions The Smart Way

  15. #15
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    no, i was told by my supervisor that i was meant to write f1 as a function of i when it was in the loop!
    can you at least tell me which bit is wrong, the float f1(....) or the f1(...) bit?

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