Printable View
I am a C beginner. I just created a program that iterates over the length of a string that calls toupper() on each character.
My question: I want to create a copy of the original, translate that and then return a pointer to the translated copy... and I am having troubles.
Anyone up for helping?
Thanx.
i can't help if you don't show your code and explain what the problem is.
ok sry, I am also on a mac. This is the code:Quote:
Originally Posted by Meldreth
There aren't any problems, i just want to learn how to use the function of toupper() in a fancier way. A friend said i could have it create a copy of the original, translate that and then return a pointer to the translated copy... but as a beginner I am confused by this. Friend is currently out of pocket.Code:#include <stdio.h>
main()
{
char firstname[80];
int loop =0;
printf(" Enter your name in lowercase letters: \n");
scanf(" %s", firstname);
for(; firstname[loop] != 0; loop ++ )
firstname[loop] = toupper(firstname[loop]);
printf("Your name in uppercase letters is: %s\n", firstname);
}
there's nothing fancy about c. your friend just means to copy the string before converting the case. it doesn't do anything but add an extra step that you probably don't need.
Code:#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
char *sdup(char* s);
char *supper(char *s);
int main()
{
char s[80], *p;
printf("enter a string> ");
fgets(s, 80, stdin);
fputs(s, stdout);
p = supper(s);
fputs(p, stdout);
free(p);
return EXIT_SUCCESS;
}
char *sdup(char* s)
{
char *p = malloc(strlen(s)+1);
return strcpy(p, s);
}
char *supper(char *s)
{
char *p = sdup(s);
int i;
for (i = 0; p[i]; i++) p[i] = toupper(p[i]);
return p;
}
Meldreth: Being pedantic, but:
You declare and define a funciton called "sdup", then call strdup() which is a non-standard but common library function.
Also, I very much prefer a variant where you pass in the receiving string, e.g.
The maxlen parameter is there to prevent buffer overflows.Code:char *supper(const char *in, char *out, int maxlen)
{
char *s = out;
while(*in && s - out < maxlen-1)
{
*s++ = toupper(*in);
in++;
}
*s = 0;
return out;
}
The advantage here is that the user has the choice of using a dynamically, stack or static allocation for the receiving variable. Returning the original is useful if you want to do stuff like:
--Code:char something[100];
char temp[4];
const char *abc = "abc";
strcpy(something, abc);
strcat(something, supper(abc, temp, sizeof(temp)));
Mats
as a beginner, that coding does not flow easily. Will you repost with comments about what each line does? I want to avoid anything needing ctype.h because with my mac working in terminal, many functions are not part of the standard.
I cannot get code to compile:
Code:$ gcc -o caps caps.c
caps.c: In function ‘supper’:
caps.c:10: error: syntax error before ‘{’ token
caps.c:31: error: syntax error before ‘for’
my bad. i got tongue lashed by laserlight for using strdup before, so i changed my mind half way and didn't follow through with it. i fixed it.Quote:
Originally Posted by matsp
ctype.h is part of the standard library, and as such, should work on Mac, Linux, Windows, OS/2, Solaris and just about any other mainstream (and many not-so-mainstream) OS you can think of.Quote:
Originally Posted by likewise
Since I can't see anything directly wrong in the code posted, it's probably best if you post what you are trying to compile, and we can probably help you out.
--
Mats
I would love to understand what yall are talking about, can you post with a more kindergarten style so the beginner can learn?
after trying to complie:Code:#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
char *sdup(char* s);
char *supper(char *s)
int main()
{
char s[80], *p;
printf("enter a string> ");
fgets(s, 80, stdin);
fputs(s, stdout);
p = supper(s);
fputs(p, stdout);
free(p);
return EXIT_SUCCESS;
}
char *sdup(char* s)
{
char *p = malloc(strlen(s)+1);
return strcpy(p, s);
}
char *supper(char *s)
{
char *p = strdup(s);
int i;
for(i = 0; p[i]; i++)
p[i] = toupper(p[i]);
return p;
}
Code:$ gcc -o caps caps.c
caps.c: In function ‘supper’:
caps.c:10: error: syntax error before ‘{’ token
caps.c:31: error: syntax error before ‘for’
your code is already kindergarten style. you asked for something fancier, and that's what malloc does for you. i also fixed the code in my first post, so you can try it again.
ok noted the error in yalls replys. fixed and it compiles.. but i still don't unerstand why. can you add comments describing what each line preforms?
im not asking for kindergarten code, im asking for you to explain what the code does to me as a beginner.
It would be better if you asked for comments on lines that are particularly difficult for you to understand - commenting thirty or so lines of code, when there are perhaps 5 that you don't understand is a waste of EVERYONE's time.Quote:
Originally Posted by likewise
--
Mats
yes i can.Quote:
Originally Posted by likewise
Code:#include <stdio.h> /* pastes contents of stdio.h to here */
#include <stdlib.h> /* pastes contents of stdlib.h to here */
#include <string.h> /* pastes contents of string.h to here */
#include <ctype.h> /* pastes contents of ctype.h to here */
/* blank line */
char *sdup(char* s); /* declares a function called sdup */
char *supper(char *s); /* declares a function called supper */
/* blank line */
int main() /* definition of main */
{ /* opening curly brace */
char s[80], *p; /* declare an array of 80 char and a pointer to char */
printf("enter a string> "); /* print something cool */
fgets(s, 80, stdin); /* make the user type a string, up to 80 characters */
fputs(s, stdout); /* print the string the user typed */
p = sdup(s); /* make a copy of the string the user typed */
fputs(supper(p), stdout); /* convert the copy to upper case and print it */
free(p); /* let the dynamic memory go back to the process */
return EXIT_SUCCESS; /* return succes */
} /* closing curly brace */
/* blank line */
char *sdup(char* s) /* definition of sdup, copies strings */
{ /* opening curly brace */
char *p = malloc(strlen(s)+1); /* dynamically allocate strlen(s)+1 bytes */
return strcpy(p, s); /* copy the string contained by s into the memory at p and return it */
} /* closing curly brace */
/* blank line */
char *supper(char *s) /* definition of supper, copies a string to upper case */
{ /* opening curly brace */
char *p = sdup(s); /* copy the string s */
int i; /* int i */
for (i = 0; p[i]; i++) p[i] = toupper(p[i]); /* convert the string to upper case */
return p; /* return the copy */
} /* closing curly brace */
Oh! Meldreth, thank you soooo much!! That is very helpful, I really appreciate your time in doing that.
that's weird. i don't usually get words of thanks when i give a super sarcastic answer...
Then you didn't understand how much of a beginner I was.
So, can you explain HOW supper() works now?Quote:
Originally Posted by likewise
--
Mats
No I cannot, but I have a start. I was looking for help, not an aggressive attack of sarcasm to put me down. Which makes me think the both of you have insecurities of some measure where you feel the need to protect yourself with sarcastic remarks that only let the world see a superficial part of who you are.
I am a beginner, 100% and if you do not want to waste your time with me, then please don't.
oh, i'm sorry i tried to help you then. i won't make that mistake again. :rolleyes:
If you want careful, detailed explanations of things, why are you on a forum (where you can get anything you want except careful, detailed explanations -- no one wants to type that much and end up just typing up the first 15 pages of a C textbook)? We can help with short, specific questions easily, because they have nice short answers; we can point you to things to read if you want things to read (see e.g. the book sticky on the top of the forum). We're not going to type up a chapter of a book into this little box just for you, though.Quote:
Originally Posted by likewise
And don't worry -- the sarcasm is not to put you down, but point up the futility of the request (it's just as impossible to read way-overly-commented code as uncommented code). No one here is taking this personally, even me.
This is a cross post :(
I don't think I have made sarcastic comments - I honestly wanted to know if you had actually gained understanding from the comments posted. However, I expect this comment is in vain, as you appear to have found some other people to try to get meaningful comments out of.Quote:
Originally Posted by likewise
--
Mats
Rule number 1) Don't cross-post or we're wasting our time.