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Re: st: Beware of Stata's Syntax


From   Maarten buis <maartenbuis@yahoo.co.uk>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Beware of Stata's Syntax
Date   Fri, 23 May 2008 09:27:23 +0100 (BST)

--- Sergiy Radyakin <serjradyakin@gmail.com> wrote:

> Thank you Austin.It follows that by default -syntax- will add an
> additional option (varlist=* max=1) which renders -syntax-
> inoperable.
> This makes it a poor choice for defaults, since most users probably
> work with datasets with more than one variable. And it makes even
> less
> sense when "varname" is in [ ].
> 
> As for the documentation , I thought when I type
> 
> StataBug x y z, option1(value1)
> 
> this would be exactly the line that is going to the parser, and after
> that x y and z are put to the -varlist-.
> 
> 
> So that if I type
> StataBug ,option1(value1)
> 
> and StataBug contains
> syntax [varname], option1(string)
> 
> Stata converts the string to be parsed into:
> "[varlist min=0 max=1], option1(string)"
> 
> substitutes from what I have typed:
> "[min=0 max=1], option1("value1")"
> 
> evaluates, must result in OK, because 0 is between 0 and 1
> 
> then fills in varlist with the variable names (if specified) or all
> variable names (if not specified) and let's the program go.
> 
> Adding * to varlist and adding (max=1) should be mutually exclusive,
> since together they will fail most of the time.
> 
> Best wishes,
>    Sergiy
> 
> 
> 
> 
> 
> 
> On 5/22/08, Austin Nichols <austinnichols@gmail.com> wrote:
> > Sergiy Radyakin <serjradyakin@gmail.com> et al. --
> >
> > Beware of posts with the word "bug" as they usually describe a
> > misunderstood feature.
> >
> > help syntax##description_of_varlist
> >
> > documents that
> >
> > The default is to fill [varlist] in with all the variables.  If
> > default=none is specified, it is left empty.
> >
> > Since
> >  Typing varname
> >    is equivalent to typing varlist(max=1).
> >
> > using either
> >
> > syntax [varname (default=none)]
> >
> > or
> >
> > syntax varname
> >
> > is safest.
> >
> > On Thu, May 22, 2008 at 5:17 PM, Sergiy Radyakin
> <serjradyakin@gmail.com> wrote:
> > > Dear All,
> > >
> > > I wonder if this is an intended behaviour (quite dangerous from
> my
> > > point of view) or just a bug?
> > >
> > > // --- Begin of file SyntaxBug.do ---
> > >
> > > program drop _all
> > > drop _all
> > >
> > > generate VariableThatShouldNotBeUsed=.
> > >
> > > program define SyntaxBug
> > >    syntax [varname]
> > >    di `"`varlist'"'
> > > end
> > >
> > > SyntaxBug
> > >
> > > generate JustAnotherVariable=.
> > >
> > > SyntaxBug
> > >
> > > // --- End of file SyntaxBug.do ---
> > >
> > > If this is not an intended behaviour then it is actually two bugs
> in
> > > one, since under some conditions the program will process the
> variable
> > > that the user DID NOT specify (first call in the program above),
> and
> > > under other conditions it will refuse to work though it
> supposedly
> > > should (second call in the program above).
> > >
> > > If this is intended (may be there is an explanation) then it goes
> > > against the documentation, saying anything in [ ] is optional.
> > >
> > > Thank you,
> > >    Sergiy Radyakin
> > *
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> 


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

visiting address:
Buitenveldertselaan 3 (Metropolitan), room Z434

+31 20 5986715

http://home.fsw.vu.nl/m.buis/
-----------------------------------------


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