Question

/*
 * PURPOSE
 *      Search if a string contains a string and print it out from there
 */
#include <stdio.h>

void searchHaystack(char cHaystack[], char cNeedle[]);
void showResult(int iOffset, char cHaystack[]);

int main() {
    // Declarations
    char cHaystack[50], cNeedle[50];

    // Input
    puts("Haystack:");
    gets(cHaystack);
    puts("Needle:");
    gets(cNeedle);

    // Call searcher
    searchHaystack(cHaystack, cNeedle);

    return 0;
}

void searchHaystack(char cHaystack[], char cNeedle[]) {
    // Declarations
    int iCntr, iCntr2, iFoundOffset;

    // Search the haystack for the first letter of the needle
    for (iCntr == 0; iCntr < 50 && cHaystack[iCntr] != '\0'; iCntr++) {
        if (cHaystack[iCntr] == cNeedle[0]) {
            iFoundOffset = iCntr;
            for (iCntr2 == 1; iCntr2 < 50 && (cHaystack[iCntr+iCntr2] == cNeedle[iCntr2] || cNeedle[iCntr2] == '\0'); iCntr2++) {
                if (cNeedle[iCntr2] == '\0') {
                    showResult(iFoundOffset, cHaystack);
                }
            }
        }
    }
}

void showResult(int iOffset, char cHaystack[]) {
    int iCntr;

    // Print the substring char by char
    for (iCntr == iOffset; iCntr < 50 && cHaystack[iCntr] != '\0'; iCntr++) {
        printf("%c", cHaystack[iCntr]);
    }
    printf("\n");
}

Looking at my debugger I noticed that cHaystack[] and cNeedle[] aren’t passed to searchHaystack properly as only the first char is conserved. How do I fix this? I haven’t learned about pointers yet.

Also, I’m getting this warning on all three for loops:

statement with no effect

What’s up with that?

Answer 1

Actually, the entire array IS being passed, the debugger only shows the first char by default because in C, the system does not know the size of an array. It is something the program has to keep track of. Since you are using strings though, which are typically null terminated, try setting the watch variable “(char*)cHaystack” (without quotes) and see what the debugger shows then.

Also, assignment statements should have one = sign, not the double == sign. So:

for (iCntr = 0; ...

Should be used, NOT:

for (iCntr == 0; ...

Same with the other for loops.