Problem With Declaring Variables In A Function
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Thread: Problem With Declaring Variables In A Function

  1. #1
    Join Date
    Dec 2005
    Posts
    251

    Problem With Declaring Variables In A Function

    This is a c program that is failing to compile. The error occurs in the calcLabs() function. The error called out is (btw, I'm using VS 2010): Error 4 error C2143: syntax error : missing ';' before 'type'

    I don't understand why the compiler is not letting me declare variables in the calcLabs() function!

    Code:
    #include<stdio.h>
    #include<stdlib.h>
    
    void calcPercent(double *);
    double calcLabs();
    double calcExams();
    double calcFinal();
    char calcLetter(float);
    
    main()
    {
    	
    	char fullname[16];
    	double perGrade = 100;
    	char letGrade = 'A';
    	int scount = 0;
    	FILE * fptr;
    	fptr = fopen("grades.txt", "w");
    	if(fptr == NULL)
    	{
    		//message exit
    	}
    	fprintf(fptr, " GRADES REPORT\n\n" );
    	fprintf(fptr, " NAME              %%GRADE          LETTER\n" );
    
    	printf("\n Enter a student or 0 to exit: ");
    	scanf("%15[^\n]s", fullname);
    	fflush(stdin);
    	while(fullname[0]!='0')
    	{
    		printf("\n Processing ...");
    		calcPercent(&perGrade);
            //calcLetter();
    		fprintf(fptr, "\n %-16s%9.2f%4c ", fullname, perGrade, letGrade);
    		scount++;
    		printf("\n Enter a student or 0 to exit: ");
    	    scanf("%15[^\n]s", fullname);
    		fflush(stdin);
    	}
    	fprintf(fptr, "\n\n Student count is %d ", scount);
    	fclose(fptr);
    	
    	return(0);
    
    }
    
    void calcPercent(double * ptr_perGrade)
    {
    	double labTotal;
    	double examTotal;
    	double finalTotal;
    	labTotal = calcLabs();
    	examTotal = calcExams();
    	finalTotal = calcFinal();
    	//*ptr_perGrade = labTotal+examTotal+finalTotal;
    }
    
    double calcLabs(void)
    {
    	printf("Got here calcLabs");
    	double score = 0.0; // THIS IS THE LINE CALLED OUT IN THE ERROR
    /**	double sum = 0.0;
    	double average = 0.0;
    	double result = 0.0;
    	for(int i = 0; i < 8; i++)
    	{
    		printf("\n Enter Lab: ");
    		scanf("%f", &score);
    		sum += score;
    	}
    	average = sum / 8;
    	result = average * .4;
    **/
    	return 0.0;
    }
    
    double calcExams()
    {
    	printf("Got here calcExams");
    	return 0.0;
    }
    
    double calcFinal()
    {
    	printf("Got here calcFinal");
    	return 0.0;
    }
    
    char calcLetter()
    {
    	printf("Got here calcLetter");
    	return 'a';
    }

  2. #2
    VictorN's Avatar
    VictorN is offline Super Moderator Power Poster
    Join Date
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    Location
    Wallisellen (ZH), Switzerland
    Posts
    17,610

    Re: Problem With Declaring Variables In A Function

    The only error I get by compiling your code in VS 2010 (with SP1) is this one:
    Code:
    error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
    - because of the wrong signature for main(): main() must be declared as int, not void.
    Last edited by VictorN; November 12th, 2012 at 04:45 AM.
    Victor Nijegorodov

  3. #3
    Join Date
    Jul 2005
    Location
    Netherlands
    Posts
    2,016

    Re: Problem With Declaring Variables In A Function

    Edit: didn't notice this was about C, not C++.

    If I compile your code with the Comeau online compiler, I only get one error (and some warnings).
    Code:
    Comeau C/C++ 4.3.10.1 (Oct  6 2008 11:28:09) for ONLINE_EVALUATION_BETA2
    Copyright 1988-2008 Comeau Computing.  All rights reserved.
    MODE:strict errors C++ C++0x_extensions
    
    "ComeauTest.c", line 10: error: return type "int" omitted in declaration of function
              "main", so use int main() OR int main(int argc, char *argv[])
      main()
      ^
    ...
    1 error detected in the compilation of "ComeauTest.c".
    Are you sure you compiled the exact code you posted?
    Last edited by D_Drmmr; November 12th, 2012 at 12:30 PM.
    Cheers, D Drmmr

    Please put [code][/code] tags around your code to preserve indentation and make it more readable.

    As long as man ascribes to himself what is merely a posibility, he will not work for the attainment of it. - P. D. Ouspensky

  4. #4
    Join Date
    Apr 1999
    Posts
    27,446

    Re: Problem With Declaring Variables In A Function

    Quote Originally Posted by spiritualfields View Post
    This is a c program that is failing to compile.
    You need to review the rules of the 'C' language when it comes to declaring variables. The rules are not the same as C++:
    Code:
    double calcLabs(void)
    {
    	printf("Got here calcLabs");
    	double score = 0.0; // THIS IS THE LINE CALLED OUT IN THE ERROR
    In the 'C' language, all variables within a block of code must be declared before any executable statements. With C++, you can basically declare variables anywhere within the block of code, not so with 'C'.

    Correction:
    Code:
    double calcLabs(void)
    {
    	double score = 0.0; 
    	printf("Got here calcLabs");
    Note now that the declaration appears before the printf(). All variables in that block must be declared before the call to printf().

    Regards,

    Paul McKenzie

  5. #5
    Join Date
    Jan 2009
    Posts
    1,689

    Re: Problem With Declaring Variables In A Function

    Yep, the stack space has to be allocated all at once in the beginning of the scope. I'm very surprised that Visual C still does that though, almost all other C compilers allow you to have C++ style declarations of variables.

  6. #6
    Join Date
    Dec 2005
    Posts
    251

    Re: Problem With Declaring Variables In A Function

    Quote Originally Posted by Paul McKenzie View Post
    You need to review the rules of the 'C' language when it comes to declaring variables. The rules are not the same as C++: All variables in that block must be declared before the call to printf().

    Regards,

    Paul McKenzie
    Thanks! That was the problem.

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