Message from discussion Generalized tagRec?

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Date: Thu, 4 Jun 2009 17:05:16 +0600
Message-ID: <2076f2f90906040405x760e99fdj94d6ca4c4300b4ca@mail.gmail.com>
Subject: Generalized tagRec?
From: Artyom Shalkhakov <artyom.shalkha...@gmail.com>
To: flapjax@googlegroups.com
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Hello,

I was writing a small file browser in Flapjax and have encountered
a problem with tagRec: there seems to be no way to make one
dynamically created tag to depend on another dynamically created
tag's events.

What I would like to achieve is a tree with branches that
can be shown or hidden.

The tree (or rather, a forest) for testing is the parse tree of an expression
a + b * c, which is translated to JS as follows:

> [{label: 'plus', children: [
>       {label: 'a', children: []},
>       {label: 'multiply', children: [
>            {label: 'b',children: []},
>            {label: 'c',children: []}]}]}]

Here's how it is converted to HTML:

> // fun :: Forest * Maybe Hash -> Dom
> function fun(y,vis) {
>     return UL(vis || {}, map(function(x) {
>          return tagRec(['click'],
>              function(e) {
>                  var db = toggleE('block','none',e).startsWith('block');
>                  return LI(A({href:'#'+x.label},x.label),
>                                 fun(x.children, {style: {display: db}}));
>              });
>     }, y));
> }

toggleE is defined as follows:

> function toggleE(a,b,e) {
>    return e.collectE(true, function(_,y) {
>        return !y;
>    }).mapE(function(x) {return x? a : b;});
> }

The tree behaves unexpectedly, because tagRec reacts to *all*
events happening inside a LI, while it should only react to events
of A.

I think I can come up with a hack but would like to write in the
most obvious (and declarative :-)) way possible.

Could anybody help me, please?

Cheers,
Artyom Shalkhakov.

PS here's a demo: http://www.sound-city.kz/fj/tree.html