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

This is a discussion on [NEED HELP] I just can't solve this program problem! within the C Programming forums, part of the General Programming Boards category; Hi, there this one lab tutorial i need to do: The question goes like this : The program prompts the ...

  1. #1
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    Unhappy [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 !!!!!!!!!!!!!!!!

  2. #2
    and the hat of wrongness Salem's Avatar
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    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.
    If at first you don't succeed, try writing your phone number on the exam paper.
    I support http://www.ukip.org/ as the first necessary step to a free Europe.

  3. #3
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    Quote Originally Posted by Salem View Post
    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 ?????

  4. #4
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    Try escaping the asterisk, like this:

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

  5. #5
    and the hat of wrongness Salem's Avatar
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    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.
    If at first you don't succeed, try writing your phone number on the exam paper.
    I support http://www.ukip.org/ as the first necessary step to a free Europe.

  6. #6
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    Quote Originally Posted by frodonet View Post
    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
    Compilers can produce warnings - make the compiler programmers happy: Use them!
    Please don't PM me for help - and no, I don't do help over instant messengers.

  7. #7
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    Quote Originally Posted by IceDane View Post
    Try escaping the asterisk, like this:

    Code:
    while( c != '\*' )
    ...
    this one doesn't work

  8. #8
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    Quote Originally Posted by matsp View Post
    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 ???

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