Need an extra pair of eyes ....

This is a discussion on Need an extra pair of eyes .... within the C Programming forums, part of the General Programming Boards category; Hello.. I am getting compiler errors which consist of ld returned 1 exit status and 3 * [Linker error] undefined ...

  1. #1
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    Need an extra pair of eyes ....

    Hello.. I am getting compiler errors which consist of

    ld returned 1 exit status and
    3 * [Linker error] undefined reference to `check_equation'

    Code:
    // preprocessor directives
    #include <stdio.h>
    #include <stdlib.h>
    #include <ctype.h>
    #include <string.h>
    #include <malloc.h>
    #define ROWS 3 
    #define COLUMNS 4 
    #define SWAP_COUNT 4 * sizeof(float)
    
    // swaps two equations: eq1 and eq2
    #define SWAP_EQ(eq1, eq2) memcpy(temp,(eq1),SWAP_COUNT); memcpy((eq1),(eq2),SWAP_COUNT);memcpy((eq2),temp,SWAP_COUNT)
    
    // multiplies two equations by the coefficients of variable var to eliminate var in equation eq
    #define MULT_EQ(var,eq) for(j = 0; j < 4; j++) {temp[0][j] = matrix[(var)][j] * matrix[(eq - 3)][(var)]; temp[1][j] = matrix[(eq - 3)][j] * matrix[(var)][(var)];} 
    
    // eliminates the variable var in equation eq by subtracting the two equations in MULT_EQ
    #define ELIM_VAR(eq) for(j = 0; j < 4; j++) matrix[(eq - 3)][j] = temp[0][j] - temp[1][j] 
    
    // function prototypes  
    
    // IN
    // returns void and has one argument
    void get_equations(float**matrix); // function that returns void and has one argument: float pointer to a pointer matrix named matrix.
    
    // IN
    // returns void and has one argument
    void format_string(char*string); // function that returns void and has one argument: a character pointer named string.
    
    // IN
    // returns an integer flag 1 or 0 and has one argument
    int check_equation(char*string); // function that returns an integer flag 1 or 0 and has one argument: a character pointer named string.
    
    // IN
    // returns void and has one argument
    void validate_equations(float**matrix); // function that returns void and has one argument: float pointer to a pointer matrix named matrix.
    
    
    //IN
    // returns void and has one argument
    void eliminate_variables(float**matrix); // function that returns void and has one argument: float pointer to a pointer matrix named matrix.
    
    
    
    int main() // returns an int
    {
         // declare and initialize variables
    
         int j;                                                                     // loop counter   
         float **matrix;                                                            // pointer matrix that holds the numberical coefficienets of the equations
         float x,y,z;                                                               // equations variables. 
         
         
         matrix = (float **) malloc(ROWS * sizeof(float **));
         
         if(matrix == NULL)                                                         // or if (matrix == NULL)
         {
    	                                                                            
    	            printf("\nError - Memory allocation failure");                  // display error message
    	            exit(1);                                                        // abort the program
         }
    
         
        for(j = 0;j < ROWS; j++)
        {
                           
           matrix[j] = (float *) malloc(COLUMNS * sizeof(float));
           if(matrix[j]== NULL)                                                     // or if (matrix[j] == NULL)
           {
    	                                                                            // display error message
    	              printf("\nError - Memory allocation failure");
    	              exit(1);                                                      // abort the program
           }       
    
         }  
         
         get_equations(matrix);
         validate_equations(matrix);
         eliminate_variables(matrix);
         x = matrix[0][3] / matrix[0][0];
         y = matrix[1][3] / matrix[1][1];
         z = matrix[2][3] / matrix[2][2];
         printf("x= %.2lf  y= %.2lf  z= %.2lf" , x, y, z);                          // come back when I define get equations
              
         system("pause");
         for(j = 0; j < ROWS; j++)
         {
               free(matrix[j]);
         }                                                                 // note only one statment so there was no need for {}
         
         free(matrix);
         system("pause");
         return 0;
    
    
    }         // This is the end of main
    
    
    
    
    // IN
    
    // Descipitions 
    
    void get_equations(float**matrix)
    {
    
         int j, k;
         char *string;
         int flag;
         
         string = (char *) malloc(35 * sizeof(char));
         if(string == NULL)                                                         // or if (matrix[j] == NULL)
         {
    	                                                                            // display error message
    	              printf("\nError - Memory allocation failure");
    	              exit(1);                                                      // abort the program
         }       
         
         GET_EQUATION_1:
         
         printf("\nEnter 1st linear 3-variable equation e.g. x+4y-6z=20:");
         fgets(string,80, stdin);
         if(check_equation(string) != 1)
              goto GET_EQUATION_1;
         format_string(string);
         sscanf(string, "%fx%fy%fz=%f", &matrix[0][0], &matrix[0][1], &matrix[0][2], &matrix[0][3]); 
         
         GET_EQUATION_2:
         
         printf("\nEnter 2nd linear 3-variable equation e.g. x+4y-6z=20:");
         fgets(string,80, stdin);
         
         
         
         if(check_equation(string) != 1) 
               goto GET_EQUATION_2;
         format_string(string);
         
         sscanf(string, "%fx%fy%fz=%f", &matrix[1][0], &matrix[1][1], &matrix[1][2], &matrix[1][3]); 
         
         GET_EQUATION_3:
         
         printf("\nEnter 3rd linear 3-variable equation e.g. x+4y-6z=20:");
         fgets(string,80, stdin);
         if(check_equation(string) != 1) 
               goto GET_EQUATION_3;
         format_string(string);
         sscanf(string, "%fx%fy%fz=%f", &matrix[2][0], &matrix[2][1], &matrix[2][2], &matrix[2][3]); 
         printf("\n\nEquation Matrix:\n\n");
         for(j=0; j < ROWS; j++)
         {
                  for(k=0; k < COLUMNS; k++)
                  {
                          printf("%.2f\t", matrix[j][k]);
                  }         
         
                  printf("\n\n");
         }
         free(string);
         
    }   // end of function
    
    
    
    // format string
    
    
    void format_string(char *string)
    {
    	unsigned int j, k;
        
        for(j = 0; j < strlen(string); j++)
    	{
    		if(string[j] == ' ')
    		{
                for(k = j; k < strlen(string) - 1; k++)
    			{
                      string[k] = string[k + 1];
                }  
            }        
    	}
    	for(j = 0; j < strlen(string); j++)
    	{
    	    if(isalpha(string[j]) && j == 0)    // may be wrong
    		{
    			for(k = strlen(string) + 1; k > j; k--) // decrements by 1 ??
    			{
                      string[k] = string[k - 1];
                }   
                      string[j] = '1';
    		}
    
    		if((string[j] == '+' || string[j] == '-') && isalpha(string[j + 1])) // may be wrong
    		{
    		   for(k = strlen(string) + 1; k > j; k--) // not sure if I have decremented by 1 
    		   {
                     string[k] = string[k - 1];
    		   }
                     string[j + 1] = '1';
    		}
    	}
    } // end format_string( )
    
    
    int check_equations(char*string) 
    {
        unsigned int j;
        int x, y, z, equals, operators, equal_found;
        x = 0;
        y = 0;
        z = 0;
        equals = 0;
        operators = 0;
        equal_found = 0;
           
        
        for(j=0; j < strlen(string); j++)
        {
             string[j] = tolower(string[j]);
             if(string[j] == 'x')
             x++;
             if(string[j] == 'y')
             y++;
             if(string[j] == 'z')
             z++;
             if(string[j] == '=')
             {
                   equals++;
                   equal_found = 1;
             }      
             if((string[j] == '+' || string[j] == '-') && equal_found == 0 && j != 0) 
                   operators++;
        }  
        
        if(x*y*z == 0 )
        printf("\nEquation must contain all variables even if cofficients are zero.\n");
        
        if(x > 1 || y > 1 || z > 1)  
        printf("\nEquation must not contain duplicate variables.\n"); 
        
        if( equals != 1)
        {
            printf("\nEquation must contain one and only one equal sign\n"); 
            equals = 0;
        }
        if(operators != 2)
        {
            printf("\nEquation has too few or too many +/- operators\n"); 
            operators = 0;
        }
        else 
        operators = 1;
        
        return x * y * z * equals * operators;
    
    }
    
    
    void validate_equations(float**matrix) 
    {
         int j;
         float temp[4];
         
         if((matrix[0][0]/matrix[1][0] == matrix[0][1]/matrix[1][1] && matrix[1][0]/matrix[1][1] ==
             matrix[0][2]/matrix[1][2] && matrix[0][2]/matrix[1][2] == matrix[0][3]/matrix[1][3]) ||
            (matrix[0][0]/matrix[2][0] == matrix[1][0]/matrix[2][1] && matrix[1][0]/matrix[2][1] ==
             matrix[0][2]/matrix[2][2] && matrix[0][2]/matrix[2][2] == matrix[0][3]/matrix[2][3]) ||
            (matrix[1][0]/matrix[2][0] == matrix[1][1]/matrix[2][1] && matrix[1][1]/matrix[2][1] ==
             matrix[1][2]/matrix[2][2] && matrix[1][2]/matrix[2][2] == matrix[1][3]/matrix[2][3]))
          //a0/a1==b0/b1&& b0 /b1 == c0/c1 && c0/c1 ==d0/d1) 1 to 2
         {
                      printf("\nOne or more equations are multiples and cannot be solved\n\n");
                      system("pause");
                      exit(-1);     
         }
    
    
         if((matrix[0][0]/matrix[1][0] == matrix[0][1]/matrix[1][1] && matrix[1][0]/matrix[1][1] ==
             matrix[0][2]/matrix[1][2] && matrix[0][2]/matrix[1][2] != matrix[0][3]/matrix[1][3]) ||
            (matrix[0][0]/matrix[2][0] == matrix[1][0]/matrix[2][1] && matrix[1][0]/matrix[2][1] ==
             matrix[0][2]/matrix[2][2] && matrix[0][2]/matrix[2][2] != matrix[0][3]/matrix[2][3]) ||
            (matrix[1][0]/matrix[2][0] == matrix[1][1]/matrix[2][1] && matrix[1][1]/matrix[2][1] ==
             matrix[1][2]/matrix[2][2] && matrix[1][2]/matrix[2][2] != matrix[1][3]/matrix[2][3]))
        //a0/a1==b0/b1&& b0 /b1 == c0/c1 && c0/c1 !=d0/d1
         {
                      printf("\nOne or more equations are inconsistent and cannot be solved\n\n");
                      system("pause");
                      exit(-1);     
         }
    
         if((matrix[0][0]+ matrix[1][0] == matrix[2][2] && matrix[0][1] + matrix[1][1] == matrix[2][1] &&
             matrix[0][2]+ matrix[1][2] == matrix[2][2] && matrix[0][3] + matrix[1][3] == matrix[2][3]) ||
            (matrix[0][0]+ matrix[2][0] == matrix[1][2] && matrix[0][1] + matrix[2][1] == matrix[1][1] &&
             matrix[0][2]+ matrix[2][2] == matrix[1][2] && matrix[0][3] + matrix[2][3] == matrix[1][3]) || 
            (matrix[1][0]+ matrix[2][0] == matrix[0][2] && matrix[1][1] + matrix[2][1] == matrix[0][1] &&
             matrix[1][2]+ matrix[2][2] == matrix[0][2] && matrix[1][3] + matrix[2][3] == matrix[0][3]))
            //a0 + a1 == c2 && b0 + b1 == b2 && c0 + c1 == c2 && d0 + d1 == d2
         {
                      printf("\nEquations are not linearly independent and cannot be solved\n\n");
                      system("pause");
                      exit(-1);     
         }
         if( matrix[0][0] * matrix[1][1] * matrix[2][2] != 0)
         {
             // do nothing
         }
         else if( matrix[0][0] * matrix[2][1] * matrix[1][2] != 0)   
         {
               SWAP_EQ(matrix[2],matrix[3]);     
         }
         else if( matrix[1][0] * matrix[2][1] * matrix[0][2] != 0)
         {
               SWAP_EQ(matrix[1],matrix[2]);
         }      
         else if( matrix[1][0] * matrix[0][1] * matrix[2][2] != 0)   
         {
               SWAP_EQ(matrix[1],matrix[2]);     
         }
         else if( matrix[2][0] * matrix[0][1] * matrix[1][2] != 0)
         {
               SWAP_EQ(matrix[2],matrix[3]);
               SWAP_EQ(matrix[1],matrix[2]);
         } 
         else if( matrix[2][0] * matrix[1][1] * matrix[0][2] != 0)   
         {
               SWAP_EQ(matrix[1],matrix[3]);     
         }
         else
         {
               printf("\nError: Insufficient number of variable coefficients to solve the equations\n\n");
               abort ();
         }                 
    }
    
    
    
    void eliminate_variables(float**matrix)     
    {
         int j;
         float temp [2][4];
         enum words {var_x = 0, var_y = 1, var_z = 2, eq_1 = 3, eq_2 = 4, eq_3 = 5};
             
         MULT_EQ(var_x, eq_2);
         ELIM_VAR(var_x);
         
         MULT_EQ(var_x, eq_3);
         ELIM_VAR(var_x);
         
         MULT_EQ(var_y, eq_1);
         ELIM_VAR(var_y);
         
         MULT_EQ(var_y, eq_3);
         ELIM_VAR(var_y);
         
         MULT_EQ(var_z, eq_1);
         ELIM_VAR(var_z);
         
         MULT_EQ(var_z, eq_2);
         ELIM_VAR(var_z);
         
    }
    Please excuse the loose formatting .. I will be cleaning this up before I submittal. But does anyone know why I am getting these errors?

    Thanks!

    WPTT

  2. #2
    Gawking at stupidity
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    You're getting the error because you prototyped and are calling check_equation() but you named the actual function check_equations().
    If you understand what you're doing, you're not learning anything.

  3. #3
    and the hat of wrongness Salem's Avatar
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    > int check_equation(char*string);
    > int check_equations(char*string)
    One of them has an extra 's'

    Can I just say 'Ugh!' to your macros!

    > #include <malloc.h>
    malloc is in stdlib.h, which you include.

    You also don't need to cast malloc in C - see the FAQ
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
    I support http://www.ukip.org/ as the first necessary step to a free Europe.

  4. #4
    Gawking at stupidity
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    Code:
    //IN
    // returns void and has one argument
    void eliminate_variables(float**matrix); // function that returns void and has one argument: float pointer to a pointer matrix named matrix.
    Don't forget to clean up all the unnecessary comments.
    If you understand what you're doing, you're not learning anything.

  5. #5
    Registered User
    Join Date
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    Smile OH man...

    As the name says....

    WHO PUT THAT THERE!!!


    Thanks Guys, looking at code for hours can be a hazard!

  6. #6
    and the hat of wrongness Salem's Avatar
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    Not to mention all those floating point comparisons with == and !=
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
    I support http://www.ukip.org/ as the first necessary step to a free Europe.

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