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Question on ? "$" :

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Posted by Azrith   (15 posts)  [Biography] bio
Date Tue 04 Feb 2003 10:30 PM (UTC)  [ quote  ]
Message
Hey everyone!
I was wondering if someone could give me a little more info as to what exactly the ? "$": does in the line
filename = feof( fpList ) ? "$" : fread_word( fpList );

This line is with
filename = feof( fpList ) ? "$" : fread_word( fpList );
if ( filename[0] == '$' )
break;

Thanks!

Kyle
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Posted by Azrith   (15 posts)  [Biography] bio
Date Reply #1 on Wed 05 Feb 2003 01:24 AM (UTC)  [ quote  ]
Message
PS :)

I realize the "$" is the end of file so is it saying if $ is found then filename = EOF otherwise filename = fread_word?

Thanks!
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Posted by Nick Gammon   Australia  (18,769 posts)  [Biography] bio   Forum Administrator
Date Reply #2 on Wed 05 Feb 2003 06:56 AM (UTC)  [ quote  ]
Message
What they are saying is that a file *should* end with "$" but if it doesn't, in other words, if feof is true, then simulate that by putting a "$" into filename, otherwise read a filename from the file.

Then the subsequent test just tests for a "$" and doesn't have to test for end-of-file as well.
- Nick Gammon

www.gammon.com.au, www.mushclient.com
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Posted by Dave   Australia  (93 posts)  [Biography] bio
Date Reply #3 on Fri 07 Feb 2003 10:11 PM (UTC)  [ quote  ]

Amended on Fri 07 Feb 2003 10:13 PM (UTC) by Dave

Message
The ? and : thing is called the ternary operator, and it's a short-hand form of a simple if-then-else. For example:
filename = feof(fpList) ? "$" : fread_word(fpList);
Could be written as:
if (feof(fpList))
    filename = "$";
else
    filename = fread_word(fpList);
Like many things in C, the ternary operator can be abused. I've seen massively-nested ?:'s which, while amusing, were certainly unreadable. For more information, google for "ternary operator".

Hope this helps,

Dave
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Posted by Azrith   (15 posts)  [Biography] bio
Date Reply #4 on Sun 09 Feb 2003 01:49 AM (UTC)  [ quote  ]
Message
Thanks for all the help everyone :)
Ya I remember going over this a long time ago I had just forgotten.

Thanks again!
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