Thread: recursive list functions

Hi guys,
Can anyone see where I'm going wrong with this, I'm hopeless with C so considering I'm dong a module on it i'm struggling.

Code:

 
boolean wordLess(wordADT word1, wordADT word2)
{
 if (isNull(word1)==FALSE)
 {     
        if(isNULL(word2)==FALSE)
        {      
               if(word1->data)<(word2->data)) \*if word1 is              
                                                                            before2*\     
               {
                     return TRUE;
               }
               else if(word1->data)==(word2->data) \*if if first letter is
                                                  the same, check the next letter*\
               {
                     return wordLess(word->next,word2->next);
               }
          else
          {    
                return FALSE;
          }
     else
     {  
          return FALSE;
     }
 }
}




boolean wordEqual(wordADT word1, wordADT word2)

 if (isNull(word1)==FALSE)
 
  if(isNULL(word2)==FALSE)
  
   if(word1->data)==(word2->data))
   
   return TRUE;
   
   else
    
     return wordEqual(word->next,word2->next);
    
   else
    
      return FALSE;
    
  
 else
  
    return FALSE;

I've not compiled them but I've got a feeling theyre wrong.
Cheers guys */

uh... what the problem with code tags?
its simple
'['code']'
blah
'['/code']'

(without the 's)

and note there is an edit option - no need to create new posts.
plz reformat your code

Well your post completely lacks any
- code tags
- indentation
- curly braces

Please use [code][/code]Tags

well > sould be < in the comparission in word less


your functions will always return false.
in case your about to compare the last element, then the next compare would match against NULL - thus returning false
since you call compare again upon reaching the end of your list

oh - i talked nonsense - forget my previous post
the function returns true if there is just ONE match.

well what do you want it to do?

right, I think wordLess is working now.
Do you think it will work? I just need to do the comments for it.

Well wordLess is looking about right now (logically), all you need do now is make it compile.

Originally Posted by sam.woolner

I'm still thinking that in the case that the words are the same it will keep recursively calling wordLess until it drops of the end of the word thus causing an error....
Can I write this (recursive) function more effectively using headList and tailList?

Let's clean up your code and take a look at it, shall we?

Code:

boolean wordLess(wordADT word1, wordADT word2)
{
    if( isNull( word1 ) == FALSE && isNull( word2 ) == FALSE )
    {
        if( word1->data < word2->data )
        {
            return TRUE;
        }
        else
        if( word1->data == word2->data )
        {
            return wordLess( word1->next, word2->next );
        }
    }
    return FALSE;
}

This is what you were doing, much cleaned up. What happens if one word is shorter than the other one, yet comes before it? You don't cover that case. Let's say, these words:

smile
smiles

You would get all the way to the 'e', and your first word would run out. Thus, the check for 'isNull( word1 )' would return TRUE, making your whole check default to 'FALSE'. Meaning, in your code, "smile" would not come before "smiles". Which would be incorrect.

I don't see the point though, in having a head / tale. The method you're using would work fine, provided you correctly handle all situations, such as the one I've described.

Quzah.