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From |
"Nick Cox" <n.j.cox@durham.ac.uk> |

To |
<statalist@hsphsun2.harvard.edu> |

Subject |
st: RE: RE: Should be simple yet ... how to write a function? |

Date |
Wed, 18 Feb 2009 18:00:38 -0000 |

All Stata functions, strict sense, such as -sin()- or -acos()- are implemented as part of the executable, or other hidden code, and as such their internals are not visible to the user. You are not missing that much, as you couldn't emulate that way of programming any way. You are replying to a posting by Martin Weiss, which referred you to an article which says more about functions, and also more about -egen- functions. It is accessible on-line, as the URL he gave implies. Nick n.j.cox@durham.ac.uk Fabrice Thanks to all of you for your thoughtful answers! I've learned much, including--but not restricted to--... a) that most experts agree that Stata indeed does not implement the most basic form of programming (function passing direct return values) b) that Stata has a wonderful programming language with Mata (I had read about it, but it's impressive what is a priori possible there) c) that Stata has an object oriented engine (hidden behind the class structure), whoa! What is still unclear to me is the following: Maarten suggested that I could make function returning variables, like many egen function. And the trick is simply to look into the .ado code of those _gxxx.ado functions. After looking briefly at such code, I'm still not clear about the details, but it sounds like a good idea. Then I noticed that some simple scalar function (such as acos()) appear also there in the library provided by Stata, and wondered: hey, why not just imitate what's there?! Currently, the only example I can find are Mata code. So my remaining question is therefore: I know I can write . scalar y = sin(x) So .... where is the code for such "sin" function. I tried ". which sin", and it responds that it is not a built in or ado-file. So where is it defined? Maybe that is all implemented in C code in the kernel, and then, I'm toast. But it does not hurt to ask... Martin Weiss See http://www.stata-journal.com/article.html?article=pr0007 * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**References**:**st: Should be simple yet ... how to write a function?***From:*"Fabrice" <fcaspam@yahoo.fr>

**st: AW: Should be simple yet ... how to write a function?***From:*"Martin Weiss" <martin.weiss1@gmx.de>

**st: RE: Should be simple yet ... how to write a function?***From:*"Fabrice" <fcaspam@yahoo.fr>

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