From svetosch@gmx.net Fri Jan 30 16:01:04 2009
From: Sven Schreiber <svetosch@gmx.net>
To: gretl-devel@gretlml.univpm.it
Subject:
 [Gretl-devel] Re: [Gretl-users] how to run multiple regressions at one time
Date: Fri, 30 Jan 2009 22:01:02 +0100
Message-ID: <49836A8E.3050903@gmx.net>
In-Reply-To: Pine.A41.4.58.0901292013080.315550@f1n11.sp2net.wfu.edu
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[moving this over from users to devel]

I guess what I mean is:

in a 'loop for i=1..10' expression, the index i obviously takes on
integer values, and it is clear that you have to do some type conversion
to get strings out of that. Hence in that case $i is perfectly intuitive.

However, in a 'loop foreach i peach pear plum' expression it...
(a) either looks as if i takes on the names of the series. Then why on
earth do I need to use $i instead of just plain i? Or...
(b) the index i really must be thought as looking up the id numbers of
the involved series, and hence is a number. But if series 'peach' has
id#2, then I would expect $i to give the string representation of "2".
In that case, to get back the name of 'peach' through the loop index i
in the first iteration, I would rather have a syntax like 'name(i)', or
some other prefix like '§i' or whatever. Otherwise IMHO it clashes with
the use in the standard for loops, see above, and that's what I find
confusing.

Was that understandable know, or have I maybe got it all wrong?

thanks for the patience,
sven

On 30.01.2009 02:22, Allin Cottrell wrote:
> On Thu, 29 Jan 2009, Sven Schreiber wrote:

>>> In a "foreach" loop the '$i' construction works by lookup:  it
>>> indexes into the relevant array of strings or variable names and
>>> returns entry i at iteration i.
>>>
>>> In other sorts of loops, '$i' just gives the string representation
>>> of the current index value, as if you had done
>>>
>>>   sprintf foo "%d", i
>> See I guess it's exactly this double, context-dependent, meaning
>> that I find confusing. I associate $i with string
>> representation, and then I'm all baffled why that (in a foreach
>> loop context) won't give me a string with a series name, but
>> some totally different thing.
> 
> Er, sorry, but what totally different thing?  "A string with a
> series name" is exactly what it gives you, no?
> 
> For example, in
> 
> <script>
> open data4-1
> list L = 1 2 3
> loop foreach i L
>   print $i
> endloop
> </script>
> 
> the loop part is equivalent to typing
> 
>   print price
>   print sqft
>   print bedrms
> 
> and in
> 
> <script>
> open data4-1
> list L = 1 2 3
> loop foreach i L
>   print "$i"
> endloop
> </script>
> 
> the loop is equivalent to typing
> 
>   print "price"
>   print "sqft"
>   print "bedrms"
> 
> I don't mean to be unhelpful, but I don't yet understand the
> problem.  It seems totally transparent to me ;-) (who wrote it!).
> 
> Allin.
> _______________________________________________
> Gretl-users mailing list
> Gretl-users(a)lists.wfu.edu
> http://lists.wfu.edu/mailman/listinfo/gretl-users
> 



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