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RE: st: RE: Parsing syntax in an ado file


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   RE: st: RE: Parsing syntax in an ado file
Date   Wed, 6 Feb 2008 17:59:07 -0000

Sorry, but I am not much clearer. If a user calls a command referring to
a variable that doesn't exist, it seems to me utterly reasonable for
Stata to complain. If you wish to subvert that, I think you'll need some
non-standard method, such as -if()- or -in()- options followed by
processing of problems within your program. If you're the user that's
one thing. If you have to explain this to other users, that's an extra
problem, or so it would seem. 

Nick 
n.j.cox@durham.ac.uk 

Sergiy Radyakin

Nick is not clear with what I mean by "other parameters". By "other
parameters" I mean parameters that are not listed in #1-4 in my
original posting, and these would be parameters other than Stata's
command "use" supports. As an example in the syntax statement I've
included a parameter "saving".

Nick suggests trying sequential syntax statements and using namelist
instead of varlist. This helps, but not completely. Namelist
substitutes for varlist, but I do not see similar substitutes for if
and in.

Example:

. clear
. mycommand income age using "myfile.ext" if female==1,
saving("anotherfile.ext")
female not found
r(111)

On 2/6/08, Nick Cox <n.j.cox@durham.ac.uk> wrote:
> I am not clear what you mean by "other parameters" in this context.
>
> I can't speak for the internals of -use-, but I am not clear why you
are
> dismissing -capture syntax-. That is exactly what I would try.
>
> capture syntax <syntax 1>
> if _rc syntax <syntax 2>
>
> Also, consider using -namelist- as an alternative to -varlist-. Then
> after
> -syntax- check whether the namelist is a varlist.
>
> Nick
> n.j.cox@durham.ac.uk
>
> Sergiy Radyakin
>
> I am writing an ado file and I want it to support:
> 1. varlist
> 2. using clause
> 3. if
> 4. in
> 5. Other parameters
>
> I am using syntax statement to do the job.
> syntax [varlist] [using/] [if] [in] [,clear] [SAVing(string)]
>
> The program in the ado file is supposed to
> A. do something with the parameters
> B. do something with the file specified in using (as usual, the word
> using may be omitted when varlist is empty)
> C. load another file with the specified varlist, if, and in
>
> However, since that file in C is not in the memory, (say I have no
> data in the memory at all) the call to my program fails. And this is
> reasonable, since no variables are in memory -- hence varlist may not
> be "non-empty", etc.
>
> I know I can parse the `0' macro myself with gettoken. But I am
> looking for a more elegant solution to do it.
>
> Q: How do I get the parts of the command named in the syntax even if
> some of the parts can't be evaluated at the moment? E.g. I want
> unknown_syntax_command [varlist] [using/] [if] [in] [,clear]
> [SAVing(string)]
> to fill in the local varlist with the specified string, ignoring the
> fact, that the variables with the specified  names are not present in
> the dataset, that in spans the range beyond the current max, etc...
>
> capture syntax .... either does what syntax does, or does nothing, so
> is of no use.
>
> Q2: since use is a built-in command, I can't see how the syntax is
> defined there. But it is what I would want to replicate in my ado.
>

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