passing function to a function

[Gamma_123]

I have written a function which reads Data from a file and calculates the distance between each point.

int read(float Wert1, float Wert2, char *filename);
int read(float Wert1,float Wert2, char *filename)
{


FILE *infile;
infile = fopen(filename,"r");


if (infile==NULL)
    {perror("Error:No file found");
    }
int i;
float x0,x1,quadrx,y0,y1,quadry,betr;
for(i=0;fscanf(infile,"%f %f",&Wert1,&Wert2)!=EOF;i++)
    {
    
        
        if(i>0)
        {
        x0 = x1-Wert1;
        quadrx = x0*x0;
        y0 = y1-Wert2;
        quadry = y0*y0;
        betr = sqrt(quadrx+quadry);
        printf("X1-Wert: %f\n X2-Wert: %f\n Y1-Wert: %f\n Y2-Wert %f\n",x1,Wert1,y1,Wert2);    
        printf("Abstand: %f\n",betr); 
        }
        else(printf("Anfangswert X1 %lf\n Anfangswert Y1 %lf\n",Wert1,Wert2));
        
        x1 = Wert1;        
        y1 = Wert2;
    }
int size = i;
return size ;
}

I now want to write a different function which needs the distance. Since I used floating numbers instead of an array (which was on purpose) I now want to pass my function read to another function so that all values can be used there. Is there any way of doing that in c?

[userxbw]

all programming languages that I know have the capability to pass a function into it.

int myFristFunction(int a, int b)
{
   return ( a+b);
}

int mySecondFunction(int a, int b)
{
   return (a * b);
}

int myThridFunction( int a, int b)
{

  return ( a / b);

}

//call them
int answer;
answer =  myThridFunction(myFirstFunction(2,3), mySecondFunction(4,5));

[Gamma_123]

So myThirdFunction would return 5/20 in your example right?

[userxbw]

So myThirdFunction would return 5/20 in your example right?

it is not the matter of what it will return, it is the showing of passing the return values from other functions into another function to replace data needed by another means. in other words instead of doing it this way.

int myFristFunction(int a, int b)

{
   return ( a+b);
}
 
int mySecondFunction(int a, int b)

{

   return (a * b);
}
 
int myThridFunction( int a, int b)
{
 
  return ( a / b);
 
}
 
//call them
int answer1 = myFristFunction(3,40);
int answer2 = mySecondFunction(32,22);
int answer3 =  myThridFunction(answer1, answer2);

like you asked, "

passing function to a function

because that is why it is done.

[userxbw]

here is another way you can use your functions as I see the function you posted passes in floats, and returns int. so I do not know what you're planing on doing with these.

 x1 = Wert1;         y1 = Wert2;

a little something to show you how to pass more than one value back out of your functions by other means then retrun which can only return one value.

#include <stdio.h>


void passingValuesIntoME(double *a, double *b)
{
     
    *a *= 3;
    *b *= 2;
}

double gettingResults(double a, double b)
{
        return (a * b);
}

int main(void)
{
    
double num1 = 2.3, num2 = 5.5, answer; 


printf("before function num1 = %.2f num2 = %.2f\n", num1,num2);
//returns value via the parameters 
passingValuesIntoME(&num1,&num2);

printf("after function num1 = %.2f num2 = %.2f\n", num1,num2);

//pass the returned values into another function
answer = gettingResults(num1,num2);

printf("gettingResults returned %.2f\n", answer);

return 0;
    
}

the results are this

userx@slackwhere:~/bin
$ ./passing_values_functions
before function num1 = 2.30 num2 = 5.50
after function num1 = 6.90 num2 = 11.00
gettingResults returned 75.90

[stahta01]

Example of what passing a function normally means in C; should normally only be learned/taught after covering pointers.
qsort(3): sort array - Linux man page

Tim S.

[Gamma_123]

Thanks userxbw, I think I got it now!

[userxbw]

Lets hope so... enjoy !