[Templates] manipulating lists inside MACRO not the same as outside

Wed, 6 Dec 2006 02:32:44 +0100

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Thank you very much Sergey and Paul for your detailed explanations.  I
understand why the macros behave the way they do now.

Francesc

On 12/6/06, Sergey Martynoff <sergey@martynoff.info> wrote:
>
>
>
> > I'm new at TT. After RTFMing i've tried to do macros that manipulate
> > lists and I've realized that I haven't understood how TT macros work.
> > Could you please tell me why the following constructs that look
> > equivalent to me behave so differently? What have I missed?
>
> Macros are just blocks (or templates) with simplified calling syntax. You
> should ot treat them as "functions" in prorgamming language.
>
>
> > 1) MACRO CAN'T RETURN A LIST:  I can't use a macro that expands to a
> > list in a loop. see this simple example:
>
> Yes, MACRO blocks can return only text, not compex objects. The same about
> BLOCK directives and calling other templates via INCLUDE or PROCESS. There
> is no (legal) way to return hash or array reference.
>
>
> > 2) LIST MANIPULATION: straightforward list manipulation is ignored
> > inside MACRO, i need to resort to Virtual Methods. example list = [
> > 1..5] doesn't work, I have to do list.splice + list.push inside a loop
> > like shown below:
>
> That's because of localization of global variables I MACRO blocks. Each
> time
> you call macro, all global variables get copied, and restore their values
> after macro has finished. This localization is needed to allow recursive
> macro calls. However, localization is not "deep", so you can modify any
> object (such as your list) by reference.
>
>
> > [%
> >    MACRO initialize_simple BLOCK;
> >      list = [ 6..10 ] ;
> >    END;
> > %]
>
> Try this as simplier way to replace list without creating new reference
> (not
> tested, but should work):
>
> [%
>    MACRO initialize_simple BLOCK;
>      CALL list.splice( 0, list.size, [ 6 .. 10 ] );
>   END;
> %]
>
>
> --
> Sergey Martynoff
>
>
> _______________________________________________
> templates mailing list
> templates@template-toolkit.org
> http://lists.template-toolkit.org/mailman/listinfo/templates
>

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Thank you very much Sergey and Paul for your detailed explanations.&nbsp; I understand why the macros behave the way they do now. Francesc <div>On 12/6/06, 
Sergey Martynoff &lt;<a href="mailto:sergey@martynoff.info">sergey@martynoff.info</a>&gt; wrote:<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
 &gt; I'm new at TT. After RTFMing i've tried to do macros that manipulate &gt; lists and I've realized that I haven't understood how TT macros work. &gt; Could you please tell me why the following constructs that look
 &gt; equivalent to me behave so differently? What have I missed? Macros are just blocks (or templates) with simplified calling syntax. You should ot treat them as &quot;functions&quot; in prorgamming language.
 &gt; 1) MACRO CAN'T RETURN A LIST:&nbsp;&nbsp;I can't use a macro that expands to a &gt; list in a loop. see this simple example: Yes, MACRO blocks can return only text, not compex objects. The same about BLOCK directives and calling other templates via INCLUDE or PROCESS. There
 is no (legal) way to return hash or array reference. &gt; 2) LIST MANIPULATION: straightforward list manipulation is ignored &gt; inside MACRO, i need to resort to Virtual Methods. example list = [ &gt; 1..5] doesn't work, I have to do 
list.splice + list.push inside a loop &gt; like shown below: That's because of localization of global variables I MACRO blocks. Each time you call macro, all global variables get copied, and restore their values
 after macro has finished. This localization is needed to allow recursive macro calls. However, localization is not &quot;deep&quot;, so you can modify any object (such as your list) by reference. &gt; [%
 &gt;&nbsp;&nbsp;&nbsp;&nbsp;MACRO initialize_simple BLOCK; &gt;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;list = [ 6..10 ] ; &gt;&nbsp;&nbsp;&nbsp;&nbsp;END; &gt; %] Try this as simplier way to replace list without creating new reference (not tested, but should work): 
[% &nbsp;&nbsp; MACRO initialize_simple BLOCK; &nbsp;&nbsp;&nbsp;&nbsp; CALL list.splice( 0, list.size, [ 6 .. 10 ] ); &nbsp;&nbsp;END; %] -- Sergey Martynoff _______________________________________________ templates mailing list
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</a> </blockquote></div>

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