Thread: String Comparison

Code:

const char *s1 = "LOloLOLOLOLoLOL blAh";
const char *s2 = "blah";

How can I compare the right hand side of s1 to s2, case insensitively? Is there a standard function for this, or will I need to write my own?

stricmp(), strcasecmp(), ComparString(), or whatever your compiler supports.

By compare, do you mean compare, or do you mean search for a substring?

Some implementations provide strcasecmp and strcasestr.

Compare. Similar to strnicmp, only the reverse...

Wait... so you want it to start from the end of the string and do a case insensitive comparison?

Originally Posted by master5001

Wait... so you want it to start from the end of the string and do a case insensitive comparison?

Exactly.

Mkay. Not explicitly, but you can always write your own or use strrev() and stricmp.

I think you're going to have to roll your own here.

Critic my coding, please:
It appears to work, but it looks pretty damn gross.

Code:

int strircmp(const char *s1, const char *s2) {

	// Compare right hand side of s1 with s2, case insensitively
	// Returns 0 if same, 1 if different

	int i = 0;
	int same = 1;

	for (i = (strlen(s2) - 1); i <= 0; i--) {
		if (tolower(s2[i]) != tolower(s1[strlen(s1) - (strlen(s1) - i)])) {
			same = 0;
			break;
		}
	}

	return !same;			

}

Mkay...

Originally Posted by kpreston

Critique my coding, please.
It appears to work, but it looks pretty damn gross.

Code:

int strircmp(const char *s1, const char *s2) {
 
    // Compare right hand side of s1 with s2, case insensitively
    // Returns 0 if same, 1 if different
 
    int i = 0;
    int same = 1;
 
    for (i = (strlen(s2) - 1); i <= 0; i--) {
        if (tolower(s2[i]) != tolower(s1[strlen(s1) - (strlen(s1) - i)])) {
            same = 0;
            break;
        }
    }
 
    //But how do you know which one is different in what way? :(
    return !same;            
 
}

Why are you assuming that s2 is shorter than s1? (Or is this an implicit strnircmp?)

Since strlen(s1) isn't going to change, there's no reason to compute it 2n times. Also
s1[strlen(s1)-(strlen(s1)-i)] isn't right anyway; should be s1[strlen(s1)-(strlen(s2)-i)]. Oh, and strlen(s2) isn't going to change either.

Originally Posted by master5001

Here is one from good ol' Microsoft... With some alterations to fit your specs.

Example:

Code:

/* Copyright (c) Microsoft Corporation. All rights reserved. */
#include <ctype.h>

/* Case insensitive strcmp. Non-ISO, deprecated. */
int strricmp(const char * p1, const char *p2)
{
    char c1, c2;
    const char *pe1 = p1 + strlen(p1) - 1, *pe2 = p2 + strlen(p2) - 1;
    int  v;

    do {
        c1 = *pe1--;
        c2 = *pe2--;
        v = (unsigned int) tolower(c1) - (unsigned int) tolower(c2);
    } while ((v == 0) && (p1 <= pe1) && (p2 <= pe2) );

    return v;
}

Nifty. Thank you all for the quick responses.

Originally Posted by tabstop

Why are you assuming that s2 is shorter than s1? (Or is this an implicit strnircmp?)

Since strlen(s1) isn't going to change, there's no reason to compute it 2n times. Also
s1[strlen(s1)-(strlen(s1)-i)] isn't right anyway; should be s1[strlen(s1)-(strlen(s2)-i)]. Oh, and strlen(s2) isn't going to change either.

Oops. Good catch. Didn't notice my typo.

I changed a couple lines of code real quick, kpreston. I just switched the pointer--'s to --pointers to kill a -1 else where.