Thread: funtion reuse

Hi everyone, I've just started learning C.
I'm trying to figure out one thing, if I have a program, say myprogram.c with a main and a bunch of functions in it, how could I take out function1 save it in a file say myfunction.c and have myprogram.c see function1?

I know this is a very basic question, I'm just starting out, thank you for any reply.

Regards,
Luca.

You would use a .h file...

1) Save the function(s) to their separate C page.
2) Create a new .h file with function prototypes in it
3) Include it into your main source page.

Code:

// functions.c

int add(int x, int y)
  { return x +  y; }

int multiplay (int x, int y)
  { return x * y; }

////////////////////////////////////////////////////////////////////////
// functions.h

int add(int x, int y);    // ---- Note the semicolon.
int multiply(int x, int y);


//////////////////////////////////////////////////////////////////////////
// main.c

#include "functions.h"   // --- note quotes not brackets

int x, y;

x = add(7,4);

y = multiply(3,2);

... and somehow coax the IDE to add the new .c source to the project.

Originally Posted by nonoob

... and somehow coax the IDE to add the new .c source to the project.

Thanks... I forgot to mention that.

I tried to follow the steps but I'm getting this error
"undefined reference to 'WinMain@16'" while I try to compile stringutils.c, here's the code

stringutils.c

Code:

#include <stdio.h>
#include <string.h>

#define MAXLEN 1000 /* max length of any input line */
int getline(char *, int);
char *alloc(int);

/* readlines: read input lines */
int readlines(char *lineptr[], int maxlines)
{
  int len, nlines;
  char *p, line[MAXLEN];
  
  nlines = 0;
  while((len = getline(line, MAXLEN)) > 0)
    if(nlines >= maxlines || (p = alloc(len)) == NULL)
      return -1;
    else
    {
      line[len-1] = '\0'; /* delete newline */
      strcpy(p, line);
      lineptr[nlines++] = p;  
    }  
  return nlines;    
}

/* writelines: write output lines */
void writelines(char *lineptr[], int nlines)
{
  int i;
  
  for(i = 0; i < nlines; i++)
    printf("%s\n", lineptr[i]);  
}

/* getline: get line into s, return length */
int getline(char s[], int lim)
{
  int c, i;

  i = 0;
  while(--lim > 0 && (c = getchar()) != EOF && c != '\n')
    s[i++] = c;
  if(c == '\n')  
    s[i++] = c;
  s[i] = '\0';
  return i;
} 

char * alloc(int n)
{
}

here is the header file

stringutils.h

Code:

int readlines(char *lineptr[], int nlines);
void writelines(char *lineptr[], int nlines);

I'm using Dev-C++ to edit and compile the source files

That's fine now.
Thank you very much.