# learning custom functions

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Hi everybody,

I'm not sure that I'm in the right place.

Anyway, I would like to know if it's any books or websites etc, which could help me to design some custom functions. I mean, not the "classical" explanation coming with the FMP Dev CD but how to write (practically talking) the "code" lines specially the language used etc..

They are some sites where you can download some custom functions and mainly, they work fine. But, I hate to misunderstand the code used !

So, Thank you for your help,

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Customs functions are made up of the standard functions provided in FMP and other custom functions. So you need to get a good foundation in the standard functions. I think the online help is a good place to start. "Using FileMaker 7" is good book.

One function that is used in many custom functions is the Let function. That maybe a good place to start, if you are familiar with most of the other functions.

A special feature of custom functions is recursion, the ability to use the function within itself. There is an excellent pdf file "Recursive Calculationsin FileMaker Developer 7" by Andrew Persons of Excelisys http://www.excelisys.com that explains how to make a recursive custom function with 3 examples.

Chivalry Software http://www.chivalrysoftware.com just released Function Helper for writing custom functions.

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Thank's a lot RalphL !

Your informatons are very helpful for me. It's exactly , what I was looking for

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• 2 months later...

Hello,

I have Using FileMaker 7: Special Edition and have a question about recursive functions (pg. 415). Here is there example:

[color:"blue"]RepeatText (text ; numberOfRepetitions) =

text & Case (numberofRepetitions>1; RepeatText (text; numberOfRepetitions - 1))

The book says the answer to RepeatText ("t"; 3) is ttt, but it seems like it should be tt to me. The first time through they get t and the result of RepeatText ("t"; 2). The next time through they get t and the result of RepeatText ("t"; 1). The final time though they get t. I figure that 1 is not greater than 1 (because it is equal to it) so there shouldn't be a third t. Who is right? I'm trying to learn custom functions!

Greg

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It's easy to know who is right - just try it...

But I guess you want an explanation where you went wrong:

The input to the first iteration is ( "t" ; 3 ).

The output of the first iteration is:

"t" & Case ( 3 > 1 ; RepeatText ( "t" ; 2 ))

The input to the second iteration is ( "t" ; 2 ).

The output of the second iteration is:

"tt" & Case ( 2 > 1 ; RepeatText ( "t" ; 1 ))

The input to the third iteration is ( "t" ; 1 ).

The output of the third iteration is:

"ttt" & Case ( 1 > 1 ; RepeatText ( "t" ; 0 ))

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Hi comment,

Thank you for your reply. I don't know what it was about how they phrased it... it just didn't make sense to me. It helps to spell it out thoroughly for those of us venturing into unknown territory. So far, I'd have to give the book very good marks.

Greg

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