Thank you, Alan, that solved the problem. Also thanks for the detailed
explanation.
Hopefully, I can show you why I need all that next week in Mannheim
Uli
Alan Riley wrote:
> Ulrich Kohler asked about calling Stata (including a local macro
>
> substitution) from Mata:
> > I have a Mata function which looks as follows:
> >
> > -------------------------------------lsq.mata--
> >
> > (...)
> >
> > // Mata Function to extract the substitution costs from subcost-matrix
> > void showhash(real rowvector R)
> > {
> > string scalar key1
> > st_local("key1",key1)
> > key1 = strofreal(R[1,2])
> > st_local("key1",key1)
> > stata("local hash1 = mod(`key1',197)")
> > }
> >
> > (...)
> >
> > ------------------------------------------------
> >
> > The function is part of the mata-libary lsq.mlib, which compiles without
> > problems. All other function in the library works well. However, if I run
> >
> > -showhash()- from within Mata I got the following error:
> > : R = 2,3,5,4
> > : showhash(R)
> >
> > invalid syntax
> > stata(): 3598 Stata returned error
> > showhash(): - function returned error
> > <istmt>: - function returned error
> > r(3598);
> >
> > Further investigation showed that the error is connected to the -stata()-
> > function. However, After running -showhash()- I can intactively run the
> > same
> >
> > -stata()- function without any problems:
> > : stata("local hash1 = mod(`key1',197)")
> > : stata("display `hash1'")
> >
> > 3
>
> `key1' is being substituted at compile time. That is, when
> Stata reads the lines
>
> void showhash(real rowvector R)
> {
> string scalar key1
> st_local("key1",key1)
> key1 = strofreal(R[1,2])
> st_local("key1",key1)
> stata("local hash1 = mod(`key1',197)")
> }
>
> just before they are compiled by Mata, macros are substituted.
> This, what is compiled is
>
> void showhash(real rowvector R)
> {
> string scalar key1
> st_local("key1",key1)
> key1 = strofreal(R[1,2])
> st_local("key1",key1)
> stata("local hash1 = mod(,197)")
> }
>
> And,
>
> local hash1 = mod(,197)
>
> produces a syntax error when it is executed later.
>
> The reason it works interactively afterward is that by that point
> the local macro 'key1' has already been defined, and thus what
> Mata sees is
>
> stata("local hash1 = mod(1.234,197)")
>
> (or rather, it sees whatever number was in R[1,2] and thus
> was stored in `key1').
>
> You can see the advantage of this macro substitution in
> adoupdate.ado. Type -which adoupdate- and then look at the
> file in a text editor (being careful to not modify it of course).
> Look for CMDNAME and the local macros after it, then search lower
> in the file to see how they are used. Their values get substituted,
> not at run-time, but just before the lines are compiled.
>
> Ulrich needs to protect `key1' from being substituted just
> before compilation by coding
>
> stata("local hash1 = mod(\`key1',197)")
>
> The string that will be compiled into the code to be passed to
> stata() will then literally be
>
> local hash1 = mod(`key1',197)
>
> which is what Ulrich wants.
>
>
> Alan
> ([email protected])
> *
> * For searches and help try:
> * http://www.stata.com/support/faqs/res/findit.html
> * http://www.stata.com/support/statalist/faq
> * http://www.ats.ucla.edu/stat/stata/
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* For searches and help try:
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