[NEED HELP] I just can't solve this program problem!

frodonet · 09-23-2007, 01:52 PM

Hi, there this one lab tutorial i need to do:
The question goes like this :

The program prompts the user to enter each line of text and does the conversion when the
text is entered. When an asterisk is entered, the program terminates. Assume that only
lowercase characters and space are entered.

Example execution (input text in italics):
Please enter text line: lord of the rings
LORD OF THE RINGS
Please enter text line: star wars
STAR WARS
Please enter text line: money no enough
MONEY NO ENOUGH
Please enter text line: *
Have a good day.

Ive done my program.

Here it is :

Code:

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

main ()
{
    char c, sentence[80];
    int i=0 ,array=0;
    
    while ( c != '*')
    {
    puts ("\n\nEnter a line of text :");
    while ( ( c = getchar () ) != '\n')
          sentence[i++] = c;
          
    sentence[i] = '\0';
   
    puts("\nThe Converted Text is:");
        
    while (array != (strlen (sentence) ))
    {      
         sentence[array] = toupper ( sentence[array] );
         array++;
    }  
    puts(sentence);
    
    
    }
    getchar();
}

The problem is, when i try to loop the program so that it will keep inquire the user to enter new text, it seems that my buffer doesn't get flushed. Means that if i enter a it will converts to A, and when the next line comes and i enter b, it will show AB. I tried flushall(), it doesn't work.

Second, when i loop with while ( c = ! '*'), it just doesn work, it won't terminate even when i enter asterisk (*).

Can anyone help me !!!!!!!!!!!!!!!!

**Salem** · 09-23-2007, 01:58 PM

You need to reset i back to 0 when the loop restarts.

frodonet · 09-23-2007, 02:06 PM

Quote:

Originally Posted by Salem

You need to reset i back to 0 when the loop restarts.

thanks. i've managed to settle the flushing of the memory, i need to set my i=0 and my array=0 and then its working fine.

But why when i enter asterisk (*), it doesnt terminate...is my code

while ( c != "*") correct ?????

IceDane · 09-23-2007, 02:20 PM

Try escaping the asterisk, like this:

Code:

while( c != '\*' )
...

**Salem** · 09-23-2007, 02:20 PM

Well c starts off uninitialised (one bad point), then thereafter it will always contain \n (which is the exit condition of the inner while loop).

matsp · 09-23-2007, 02:28 PM

Quote:

Originally Posted by frodonet

thanks. i've managed to settle the flushing of the memory, i need to set my i=0 and my array=0 and then its working fine.

But why when i enter asterisk (*), it doesnt terminate...is my code

while ( c != "*") correct ?????

It is syntactically correct (using single-quotes, not double quotes), but since

Code:

    while ( ( c = getchar () ) != '\n')
          sentence[i++] = c;

guarantees that the only value that c can have after this loop is '\n' [that's the value it has when it exits the loop], your outer while-loop will never see any other condition after the first iteration. The value of c at the start of the first iteration of the loop is undefined (you haven't give c a value), so it may not enter the loop if you are unlucky enough that the "random" value that c happens to have is '*'.

One solution would be that you compare the string sentence with the string-constant "*" using strcmp() - again, make sure the string is initialized, or you'll have undefined behaviour in the first iteration of the loop.

Whilst this is a "style" issue, rather than correct/incorrect code, I would prefer to see the outer loop as a "do - while" rather than "while"...

"do - while" is a "do this at least once, until < some condition > is false", so it's implicit from the code itself that you wish the content of the loop to happen AT LEAST once. It saves the reader of the code to figure out "what is the condition at the beginning of the loop at the first iteration - will this loop be entered at all?".

--
Mats

frodonet · 09-23-2007, 02:42 PM

Quote:

Originally Posted by IceDane

Try escaping the asterisk, like this:

Code:

while( c != '\*' )
...

this one doesn't work

frodonet · 09-23-2007, 02:44 PM

Quote:

Originally Posted by matsp

It is syntactically correct (using single-quotes, not double quotes), but since

Code:

    while ( ( c = getchar () ) != '\n')
          sentence[i++] = c;

guarantees that the only value that c can have after this loop is '\n' [that's the value it has when it exits the loop], your outer while-loop will never see any other condition after the first iteration. The value of c at the start of the first iteration of the loop is undefined (you haven't give c a value), so it may not enter the loop if you are unlucky enough that the "random" value that c happens to have is '*'.

One solution would be that you compare the string sentence with the string-constant "*" using strcmp() - again, make sure the string is initialized, or you'll have undefined behaviour in the first iteration of the loop.

Whilst this is a "style" issue, rather than correct/incorrect code, I would prefer to see the outer loop as a "do - while" rather than "while"...

"do - while" is a "do this at least once, until < some condition > is false", so it's implicit from the code itself that you wish the content of the loop to happen AT LEAST once. It saves the reader of the code to figure out "what is the condition at the beginning of the loop at the first iteration - will this loop be entered at all?".

--
Mats

i have tried strcmp() - doesn't work
second, the do while also doesnt work...

can you show me the modification that i need to do ???

09-23-2007, 01:52 PM	#1
frodonet Registered User Join Date: Sep 2007 Posts: 45	[NEED HELP] I just can't solve this program problem! Hi, there this one lab tutorial i need to do: The question goes like this : The program prompts the user to enter each line of text and does the conversion when the text is entered. When an asterisk is entered, the program terminates. Assume that only lowercase characters and space are entered. Example execution (input text in italics): Please enter text line: lord of the rings LORD OF THE RINGS Please enter text line: star wars STAR WARS Please enter text line: money no enough MONEY NO ENOUGH Please enter text line: * Have a good day. Ive done my program. Here it is : Code: #include <stdio.h> #include <ctype.h> #include <string.h> main () { char c, sentence[80]; int i=0 ,array=0; while ( c != '') { puts ("\n\nEnter a line of text :"); while ( ( c = getchar () ) != '\n') sentence[i++] = c; sentence[i] = '\0'; puts("\nThe Converted Text is:"); while (array != (strlen (sentence) )) { sentence[array] = toupper ( sentence[array] ); array++; } puts(sentence); } getchar(); } The problem is, when i try to loop the program so that it will keep inquire the user to enter new text, it seems that my buffer doesn't get flushed. Means that if i enter a it will converts to A, and when the next line comes and i enter b, it will show AB. I tried flushall(), it doesn't work. Second, when i loop with while ( c = ! ''), it just doesn work, it won't terminate even when i enter asterisk (*). Can anyone help me !!!!!!!!!!!!!!!!
frodonet is offline

09-23-2007, 01:58 PM	#2
Salem and the hat of Jobseeking Join Date: Aug 2001 Location: The edge of the known universe Posts: 21,710	You need to reset i back to 0 when the loop restarts. __________________ If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
Salem is offline

09-23-2007, 02:20 PM	#4
IceDane Ex scientia vera Join Date: Sep 2007 Posts: 464	Try escaping the asterisk, like this: Code: while( c != '\*' ) ...
IceDane is offline

09-23-2007, 02:20 PM	#5
Salem and the hat of Jobseeking Join Date: Aug 2001 Location: The edge of the known universe Posts: 21,710	Well c starts off uninitialised (one bad point), then thereafter it will always contain \n (which is the exit condition of the inner while loop). __________________ If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
Salem is offline

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