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Newcomers DBPro Corner / Stupid question with Constants

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bobbel
15
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Joined: 5th Jan 2009
Location: In my DBPro case xD
Posted: 24th May 2009 09:44 Edited at: 24th May 2009 09:51
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Hi all, little question about constants, this code won't let me compile!



it says "Compilation Failed (Syntax Errors)" when i try to. do you need to place constants on the top of your code or something? i looked all over the forums but i can;t find the answer...

EDIT: oops sorry, i changed the name from Left to LeftBorder, now it works... :S

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Dream And Death
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Joined: 21st Feb 2006
Location: The circus! Juggling job, kids and DBPro
Posted: 24th May 2009 11:30
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Yep, cause LEFT is a reserved keyword, being the name of a built in command. ^_^

"You get what everyone gets, you get a lifetime!" - Death, The Sandman Library

First you Dream, then you ... - Neil Gaiman, 2001
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IanM
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Posted: 24th May 2009 16:09 Edited at: 24th May 2009 16:10
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There are a couple of things you need to know about constants so that you can use them correctly.

They simply replace text in your source code, they do not pre-calculate or do anything clever at all. Because of this you can get unintended side-effects.

Before you run this code, see if you can predict what value will be printed:


If you said 50, then you've just hit the problem, because the answer is actually 35.

MyConstant*2 ==> x+10*2 ==> x + 20 ==> 35

Fix it by wrapping the replacement text in brackets:


MyConstant*2 ==> (x+10)*2 ==> (15+10)*2 ==> 25*2 ==>50

[edit]Actually, a better and clearer way to do what your original constants do, is to not use constants and use functions instead - your constants aren't really constants.

Utility plug-ins collection (updated 28/03/09) and
http://www.matrix1.demon.co.uk
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bobbel
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Location: In my DBPro case xD
Posted: 24th May 2009 17:11
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i know, thanks for explanation adn help!

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