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Program Announcements / DBPro expression evaluator plugin

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David T
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Posted: 25th Oct 2003 13:10
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Not quite a plugin (I'm not a C++ type i'm afraid) but thois does the job just as well.

This will return the answer to any expression passed to it, eg:

(4+3*(7-9))^2

Syntax:

eval(exp$)

The ZIP includes demo source and exe.

http://www.davidtattersall.me.uk/db/downloads/DBProExpEval.zip

Fishie says:
"Those who fail to prepare prepare to fail"
"Rules are for the guidance of the wise and the blind obdeniency of the fools"
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keeblerElf
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Posted: 27th Oct 2003 21:42
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Oh why oh why oh why didn't this exist about 2 months ago
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Ian T
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Posted: 28th Oct 2003 06:55
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Excellent, thank you !

--Mouse: Famous (Avatarless) Fighting Furball

A very nice %it, indeed.
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Van B
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Posted: 28th Oct 2003 14:55
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Hehe, been meaning to write one of those for years - nice one David, that's gonna be invaluable to a lot of DB'ers.


Van-B

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David T
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Posted: 28th Oct 2003 16:48
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Quote: "Oh why oh why oh why didn't this exist about 2 months ago "

Hehe it did, never got round to releasing it!

Quote: "Excellent, thank you !"


No problem

Quote: "Hehe, been meaning to write one of those for years - nice one David, that's gonna be invaluable to a lot of DB'ers."


Thanks, I got the idea when I saw how hard it was to evaluate a decent expression in DB

"The trouble with the French is that they have no word for 'entreprenuer'" - Pres. George W Bush
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Codger
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Posted: 3rd Nov 2003 17:28
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Is this not the same as Text?

text 10,10,str$((4+3*(7-9))^2)

wait key

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spooky
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Posted: 3rd Nov 2003 22:48
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Errr No.

If you have a program that builds expressions on the fly there is no way to evaluate them at present without this plugin.

So of you have built a string

s$="(4+3*(7-9))^2"

there is no native DB command to evaluate it, like other languages have.

Boo!
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Codger
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Posted: 4th Nov 2003 09:45
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Spook

text 10,10,str$((4+3*(7-9))^2)
wait key

prints "4"

what does this plugin calculate?

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spooky
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Posted: 4th Nov 2003 12:17
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It also calculates 4 but that is not the point!

DBPro will only evaluate values that are predetermined. What if program generates an expression from user input and builds a string, lets say expression$

There is no way to evaluate it without this plugin. Try it. Have line 1 as

s$="4+4"

Now try and use any of DBPro's commands to write out the result.

Boo!
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TheOneRing
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Posted: 5th Nov 2003 17:00 Edited at: 5th Nov 2003 17:07
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An interesting approach. I have tried (not too hard) to convert my expression parser I wrote in C++ to DBP. I have had difficulty, however, becuase mine relies on pointer variables, something DBP lacks good support for (at least I can't seem to get it to work right). Mine also evaluates user-defined functions as part of an expression (much like C++). What did you write it in?

Just curious...
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