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RE: st: Submitting a command in a couples of pieces


From   "Martin Weiss" <martin.weiss1@gmx.de>
To   <statalist@hsphsun2.harvard.edu>
Subject   RE: st: Submitting a command in a couples of pieces
Date   Thu, 29 Oct 2009 23:39:36 +0100

<>

Then restrain the options for the -_request()- thing to -local-s to avoid
the confusion. Most of the time, users will want to process any input
obtained via this -display- option immediately, so -local-s should be
sufficient...


HTH
Martin


-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Sergiy Radyakin
Sent: Donnerstag, 29. Oktober 2009 23:36
To: statalist@hsphsun2.harvard.edu
Subject: Re: st: Submitting a command in a couples of pieces

-levelsof- requires a name of the local, _request requires a name of a
local or a global.

from the manual:
"local(macname)         insert the list of values in the local macro
macname"
it will not save into a global.

It must be clear for Stata what the user means
Best, S.R.

On Thu, Oct 29, 2009 at 6:29 PM, Martin Weiss <martin.weiss1@gmx.de> wrote:
>
> <>
>
> " Martin, why is it unusual?"
>
> For the reasons I gave earlier. Stata`s internal handling is none of the
> user`s business (apart from a few who drill to the very bottom of things,
> not naming names...). The point is that Stata, to the best of my
knowledge,
> never demands that you prepend the underscore to the name of the -local-
> yourself... See, for instance, -levelsof-.
>
>
> HTH
> Martin
>
>
> -----Original Message-----
> From: owner-statalist@hsphsun2.harvard.edu
> [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Sergiy Radyakin
> Sent: Donnerstag, 29. Oktober 2009 22:00
> To: statalist@hsphsun2.harvard.edu
> Subject: Re: st: Submitting a command in a couples of pieces
>
> On Thu, Oct 29, 2009 at 3:20 PM, Martin Weiss <martin.weiss1@gmx.de>
wrote:
>>
>> <>
>>
>> "-_request()- will store the result in a local macro if you prefix its
> name
>> with an underscore"
>>
>> I spent most of the few minutes required for my reply wondering why I
> could
>> not get the -local- -macro- route to work. Now that Bill has pointed out
> the
>> solution, I appreciate that the last example, in [P] on p. 102, does say
>> exactly what you are supposed to do to make this work. And yet: Is it not
>> highly unusual that the user has to supply the underscore for the
-local-?
>
> Martin, why is it unusual?
>
> manual for -display- says:
> ... _request(macname) ...
> we know that the names of local macros all start with an underscore
> (check it with -macro dir- after defining some locals and globals)
> so to tell Stata whether macname means local or global you put an
> underscore.
>
> other commands may allow you to do the same. consider for example:
> . mata st_global("_mylocal","my local value")
> . display "`mylocal'"
> my local value
>
> same applies to plugins. In fact plugins do not make a difference, see
> the plugins manual: "By macros we mean both global macros and local
> macros (local to the program calling the plugin). Internally, global
> macros and local macros share the same namespace, with the names of
> local macros preceded by an underscore (_). "
>
> I believe this is a rather historical thing. Already in the Stata 5
> manual ([R] macro, p.408) we read that:"The command local is formally
> defined as equivalent to global _".
> And this text survived unchanged to the Stata 11 manual ([P] macro,
> p.194). So, if anything, it is the behaviour of the local command that
> may be surprising: it does not require an underscore.
>
> Best regards, Sergiy Radyakin
>
>
>
>> (I cannot think of another command that requires this treatment). This
> fact
>> could be given more prominence in the manual entry, as normally Stata
> would
>> prepend the underscore for you, as is obvious from:
>>
>>
>> ***
>> ma drop _allv
>> local a 1
>> ma di
>> ***
>>
>
>
****************************************************************************
> *****
> In this example, suppose you have:
>
> local a "Local"
> global a "Global"
>
> How do you list the value of the local macro a?
> Yes:
>
> macro list _a
>
> (or macro dir _a -- not sure why this works as well, but I don't mind,
> both are quite intuitive).
>
>
>
>
>>
>> HTH
>> Martin
>>
>>
>> -----Original Message-----
>> From: owner-statalist@hsphsun2.harvard.edu
>> [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of William Gould,
>> StataCorp LP
>> Sent: Donnerstag, 29. Oktober 2009 20:03
>> To: statalist@hsphsun2.harvard.edu
>> Subject: Re: st: Submitting a command in a couples of pieces
>>
>> Adrian Sayers <Adrian.Sayers@bristol.ac.uk> asks,
>>
>>> [...] i want stata to ask me a question, then i want to key the
>>> response, and then i want stata to run a program. It sounds a little
>>> pointless but i am trying read in 3000 odd data files plot them and then
>>> trim the file to the relevant section.
>>>
>>> eg.
>>>      di "What is the first day of data collection?"
>>>      Type 3
>>>      di "Day of first data collection = 3"
>>>      drop if day<3
>>
>> Martin Weiss <martin.weiss1@gmx.de> replied,
>>
>>> *************
>>>      di "What is the first day of data collection?" _request(day)
>>>      3
>>>      di "Day of first data collection =$day "
>>>      drop if day<$day
>>> *************
>>
>> Exactly right.  Let me add a few details.
>>
>> -_request()- will store the result in a local macro if you prefix its
name
>> with an underscore, so Martin's answer could have read,
>>
>>       di "What is the first day of data collection?" _request(_day)
>>       3
>>       di "Day of first data collection =`day' "
>>       drop if day<`day'
>>
>> Note that I put -_day- in the -_request()-, but even so, after that, I
>> referred to -`day'- just as I usually would.
>>
>> Here's Martin's answer put into a -program-, which might be an ado-file:
>>
>>
>>    program trythis
>>        version 11
>>
>>        di "What is the day of the data collection?  " _request(_day)
>>        di "Day of the first data collection = `day'"
>>        drop if day<`day'
>>    end
>>
>>
>> I next suggest to Adrian that if he is going to ask more than one
> question,
>> he must anticipate that users will sometimes mistype their answers.
>> Most commonly, they will hit Return before typing any answer.  As I
> result,
>> I recommend creating a subroutine to get answers:
>>
>>
>>    program trythis
>>        version 11
>>
>>        askquestion "What is the day of the data collection?"
>>        local day "`s(answer)'"
>>        di "Day of the first data collection = `day'"
>>        drop if day<`day'
>>    end
>>
>>
>>    program askquestion, sclass
>>        args last_line_of_text
>>        while (1) {
>>                di as txt "`last_line_of_text' -> " _request(_answer)
>>                if ("`answer'"=="") {
>>                        di as txt "Please answer question, or type" ///
>>                           as res "qq" as txt "to break."
>>                }
>>                else if ("`answer'"=="qq") {
>>                        exit 1
>>                }
>>                else {
>>                        sreturn local answer "`answer'"
>>                        exit
>>                }
>>        }
>>    end
>>
>> In the above code, if the user just presses Return, the question is asked
>> again.  The user can type -qq- to have the code break (stop asking
>> questions).
>>
>> If I were Adrian, I would also check the lexical class of the answer in
>> subroutine -askquestion-.  Sometimes answers can be text, even blank,
>> and other times they must be numbers, and even integers.  Adrian needs
>> to think about the types of the answers he will need.  As a simple
> example,
>> we might modify -askquestion- to allow the caller to specify one of the
>> following lexical types:
>>
>>                text          (meaning a non-blank string)
>>                number        (any number, and only a number)
>>                integer       (any number that is an integer)
>>
>> I would then construct code that looks something like this,
>>
>>    program askquestion, sclass
>>        args lex_class last_line_of_text
>>
>>        while (1) {
>>                sreturn clear
>>                askqustion_ask "`last_line_of_text'"
>>                local answer  "`s(answer)'"
>>
>>                if ("`answer'"=="qq") {
>>                        exit 1
>>                }
>>
>>                if ("`answer'"!="") {
>>                        askquestion_check `lex_class' "`answer'"
>>                        if (`"s(invalid)'"=="") {
>>                                sreturn local answer "`answer'"
>>                                exit
>>                        }
>>                }
>>                else {
>>                        di as txt "Please answer question, or type" ///
>>                           as res "qq" as txt "to break."
>>                }
>>        }
>>    end
>>
>>    program askquestion_ask, sclass
>>        args text
>>        di as txt "`text'" -> " _request(_answer)
>>        sreturn local answer "`answer'"
>>    end
>>
>>    program askquestion_check, sclass
>>        args lex answer
>>
>>        if ("`lex'"=="text") {
>>                exit
>>        }
>>
>>        if ("`lex'"=="number") {
>>                capture confirm number `answer'
>>                if (_rc) {
>>                        di "You must answer with a number"
>>                        sreturn local invalid invalid
>>                }
>>                exit
>>        }
>>
>>        if "`lex'"=="integer") {
>>                capture confirm number `answer'
>>                if (_rc) {
>>                        di "You must answer with an integer"
>>                        sreturn local invalid invalid
>>                }
>>                exit
>>        }
>>
>>        di as error "Invalid lexical class -`lex'-"
>>        di as error "caller has error"
>>        exit 198
>>    end
>>
>>
>> All that said, there's nothing wrong with Martin's original answer if
>> Adrian will only be asking a few questions and asking them of himself.
>>
>> -- Bill
>> wgould@stata.com
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