Re: st: References for `= foo'

["William Gould, StataCorp LP" <wgould@stata.com>]

Sergiy Radyakin <serjradyakin@gmail.com> wrote, 

> > If there is a function or a reference to a variable in the dataset
> > that you want to get evaluated, you place '=' in front. Be careful
> > with strings as string expressions  are subject to a rather low chars
> > limit (not sure about Stata 13).

Wayne Folta <wfolta@mac.com> replied, 

> It appears that it's longer than in the past. In Stat/IC 13 I just
> created a local macro using = and not using = that was 1700 characters
> long in both cases. If I did this correctly, this is a huge
> improvement!

Yes it is.  How many times has someone written to Statalist about their
program being broken because they coded,

                local cp = "`varlist'"

Well, that's not a problem anymore.  Stata's expression parser is now up to
working with 2-billion character strings.

In fact, you'll want to start thinking of macros as being short.  The
maximum length of a macro is a mere 1,081,511 characters.

This lead Sergiy to write, 

> Before 13 we could be sure that any value of a string variable could
> be fit into a macro, but not every macro (potentially 1 mln chars)
> could be saved into a value of a string variable (up to 244 chars).
> Now in 13 we have the reverse problem: [...]

I have a solution.  

To handle the problem of string variables not fitting into macros, we
updated string scalars in Stata 13.  String scalars can now hold
strings up to 2-billion characters long, and they can be binary to
boot.

In programs, you code

                program ...
                        version 13
                        ...
                        tempname mystr
                        ...
                        ...
                        scalar `mystr' = ...
                        ...
                        generate ... = ... `mystr' ...
                        ...
                end

That is, use string scalars to store the values of variables, name the 
scalars using the -tempname- function, and then use the temporary name
in other Stata commands just as you would have the macro, except do not 
double-quote the name. 

-- Bill
wgould@tata.com
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