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Re: st: behaviour of locals


From   Sunil Kumar <stuff.sunil@googlemail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: behaviour of locals
Date   Wed, 24 Aug 2011 12:34:22 +0100

Dear Nick,

Thank you for explaining this and clarifying what I had misunderstood.

Sunil


On Wed, Aug 24, 2011 at 12:08 PM, Nick Cox <njcoxstata@gmail.com> wrote:
> Also, the behaviour that you expect would make it possible for your
> own code to break official Stata commands if you used the same macro
> names.
>
> As it is, what -local- does is set up a _temporary_ name and then
> assign contents to it. So, the intended side-effect of that is the
> name and thus its contents fading away into oblivion at the end of a
> program.
>
> A way to fix this in mind is to understand that -local- and -global-
> are not arbitrary names, but indicate the scope of macro definitions.
>
> Nick
>
> On Wed, Aug 24, 2011 at 11:34 AM, Nick Cox <njcoxstata@gmail.com> wrote:
>> This is not an "issue". It is an intended consequence, and precisely
>> what is meant by -local-. Local macros have meaning only locally,
>> meaning within the same program, very wide sense, which means within a
>>
>> 1. program, strict sense
>>
>> 2. do file
>>
>> 3. do file editor contents
>>
>> 4. interactive session.
>>
>> So, if you run a program or do file, a local macro defined in that
>> program or do file should be considered to disappear once that
>> terminates and in any case to be utterly invisible outside it even
>> while it is running.
>>
>> There is no contradiction here. It is merely that your interactive
>> session is not over until you exit Stata.
>>
>> Your possibilities include passing the value of a local to a do file
>> or a program as an argument, using a global instead, or redefining a
>> local within each program, wide sense, that you use.
>>
>> The behaviour that you expect would make Stata very difficult to
>> manage as to use -local-s at all within your own code you would have
>> keep to track of -local- definitions within all the programs that you
>> run, including those that define or are called by official commands.
>>
>> Nick
>>
>> On Wed, Aug 24, 2011 at 11:14 AM, Sunil Kumar
>> <stuff.sunil@googlemail.com> wrote:
>>> Dear Statalisters,
>>>
>>> I'm running Stata 12.0 (update level 8th Aug 2011) on a Mac (10.6.8).
>>> My issue is that if I define a local as part of a do file, it exists
>>> only for that particular execution of the do file, but if I type it
>>> into the command window, it exists till I exit Stata, which is what I
>>> understand to be the expected behaviour.
>>>
>>> For example:
>>>
>>>  sysuse auto, clear
>>>
>>> . local test "price"
>>> . reg `test' mpg
>>>
>>> works fine if I type commands into the command window or run a do file
>>> that contains both these lines. But if I run the two commands (local
>>> then reg) separately from a do file, one by one, then the regression
>>> only includes a constant, i.e. the local is missing.
>>>
>>> Similarly, if I run the local command from a do file and type anything
>>> involving the local into the command line, then the local is still
>>> missing (blank). Am I misunderstanding how locals should behave? I've
>>> tried the same thing on Stata 11 and the local exists till I exit
>>> Stata, irrespective of whether it was defined in a do file or typed
>>> manually.
>>>
>>
>
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