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Re: st: Should be simple yet ... how to write a function?

From   Maarten buis <>
Subject   Re: st: Should be simple yet ... how to write a function?
Date   Wed, 18 Feb 2009 10:39:12 +0000 (GMT)

--- On Wed, 18/2/09, Fabrice <> wrote:
> how does one write a *function*, i.e. a program that returns
> a value, and that can be called like local y = fct(x), where
> x and y are numbers or strings. <snip>
> FYI, I know about r-type vs. e-type program, and know how to
> store results to return to main program.

Short answer: you can't.

Longer answer:

You can leave a local behind using the not documented
-c_local- command, so in the example below the program 
square leaves behind a local called foo

*------------ begin example ---------
capture program drop square
program define square
	c_local `1' = `2'^2
square foo 2
di `foo'
*------------ end example -----------

You can make a function like program that works with
the -egen- command, but this will only make variables.
To do so call your program _g<whatever>.ado, to create
the whatever "function". You can look at 
-viewsource _gcount.ado- to see an example of such a
program. Alternatively you can make a function in Mata,
but that will only function as a function within Mata.

Hope this helps,

Maarten L. Buis
Department of Social Research Methodology
Vrije Universiteit Amsterdam
Boelelaan 1081
1081 HV Amsterdam
The Netherlands

visiting address:
Buitenveldertselaan 3 (Metropolitan), room N515

+31 20 5986715


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