Path: utzoo!utgpu!news-server.csri.toronto.edu!clyde.concordia.ca!ccu.umanitoba.ca!salomon
From: salomon@ccu.umanitoba.ca (Dan Salomon)
Newsgroups: comp.lang.c
Subject: Re: Is there a good example of how toupper() works?
Message-ID: <1990Oct17.024233.16435@ccu.umanitoba.ca>
Date: 17 Oct 90 02:42:33 GMT
References: <2466@ux.acs.umn.edu>
Organization: University of Manitoba, Winnipeg, Canada
Lines: 48

In article <2466@ux.acs.umn.edu> edh@ux.acs.umn.edu (Eric D. Hendrickson) writes:
>Basically, what I want to do is take a string of upper/lower case, and make
>it all upper case.  Here is a first try at it,
>
>
>#include <ctype.h>
>main()
>{
>	char *duh = "Hello";
>	printf("%s\n", duh);
>	while (*duh <= strlen(duh)) {
>		if (islower(*duh)) *duh = toupper(*duh);
>		*duh++;
>	}
>	printf("%s\n", duh);
>}

There are at least four errors in this code.  Two of them are in your
while statement.  There is no point in repeatedly recomputing the
string length, and no point in comparing either a pointer, or the
character it points to to that length.  Instead test for the end of the
string by finding the terminating null character.  The other two
errors, incrementing the character instead of the pointer, and trying
to print the string by pointing to its end, were mentioned in earlier
postings.  Try the following version:

#include <ctype.h>
main()
{
	char *duh = "Hello";
	char *cur;

	printf("%s\n", duh);
	cur = duh;
	while (*cur) {
		if (islower(*cur)) *cur = toupper(*cur);
		cur++;
	}
	printf("%s\n", duh);
}

Sometimes it pays to stay in bed on Monday, rather than spending the
rest of the week debugging Monday's code.  :-)
-- 

Dan Salomon -- salomon@ccu.UManitoba.CA
               Dept. of Computer Science / University of Manitoba
	       Winnipeg, Manitoba  R3T 2N2 / (204) 275-6682