Re: st: RE: Double -for- loop on one line crashes Stata (resend)

[Roger Newson <roger.newson@kcl.ac.uk>]

At 17:31 15/10/02 +0100, Nick Cox wrote (in reply to Kaleb Michaud):

> I don't know if what appears in my mailer
> is exactly what you typed, but my advice
> is _never_ to place any text on a line after
> a left brace { in a loop. Always start a new
> line.
>
> Sometimes Stata can work out what you
> mean when you do that, but it is not
> guaranteed that it will be able to do so.
>
> This is perhaps tacit rather than explicit
> in documentation.
Alternatively, if you have set the command delimiter to a semicolon by using

#delim ;

then you should be able to type your code as

forvalues i =1/3 {;forvalues j=1/3 {;replace badcode = badcode + "h`i'_`j'" 
if hrec`i'_`j'chk>0; } ;};

because then a semicolon is a substitute for a carriage return (which is 
the usual command delimiter). However, even then, the program is more easy 
to read (for most people) as

forvalues i =1/3 {;
    forvalues j=1/3 {;
        replace badcode = badcode + "h`i'_`j'" if hrec`i'_`j'chk>0;
    } ;
};

Most people in the Stata community, most of the time, do not like 
multi-command lines (although multi-line commands are fairly common). And a 
right brace

}

counts as a command. And a phrase ending in a left brace, such as

forvalues i=1\3 {

also counts as a command.

Ideally, Stata is supposed to insist that commands are delimited by a 
command delimiter, which is either a carriage return or a semicolon, 
depending on which delimiter is in force. In practice, it sometimes does 
not do so. However, it is safer to use one delimiter or the other. And it 
often makes the program more legible to use both, as in the above example.

Roger


--
Roger Newson
Lecturer in Medical Statistics
Department of Public Health Sciences
King's College London
5th Floor, Capital House
42 Weston Street
London SE1 3QD
United Kingdom

Tel: 020 7848 6648 International +44 20 7848 6648
Fax: 020 7848 6620 International +44 20 7848 6620
  or 020 7848 6605 International +44 20 7848 6605
Email: roger.newson@kcl.ac.uk

Opinions expressed are those of the author, not the institution.

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