[Newbies] Re: Re: error trap

[Klaus D. Witzel]

On Wed, 09 Aug 2006 21:11:40 +0200, Ron Teitelbaum wrote:
> Brian,
>
> Yes I agree it's a great suggestion, although a few changes:
> Literal blocks to not parse into collections automatically.

Ron, please: a literal Array is a subclass of Collection and so the blocks  
in

  { [nil]. [true]. [false] }

parse "into collections automatically". You didn't inspectIt for verifying  
your (false) claim, didn't you. Also, have a look at the implementors of  
#caseOf: and #caseOf:otherwise:, they are heavy users of literal blocks in  
Collections ...

...
> Each in this case is already a block.

Yes. And, into the other direction, even in good core methods one often  
finds things like

  ^ dict at: aKey ifAbsent: [nil]

There seems to be a "natural" confusion between "object" value and block  
"value". Not a big surprise since Java and other procedural-oriented  
friends do not offer block values. So any demo of using blocks "as if"  
they where any other object, as Brian has shown, is a sign for the ability  
to master the subject 8-)

> Only each is needed.

Absolutely.

> So here is a version that works.
>
> (OrderedCollection new
> add: [10/0];
> add: [2 raisedToInteger: 1/2];
> add: [-5 raisedTo: 1.5]; yourself
> ) do: [:each | each on: Exception do: [:ex | Transcript show: ex; cr;
> endEntry]].
>
> endEntry is for Klaus!

Hhm, endEntry is too expensive within any and every loop. Just put  
Transcript endEntry after the loop. I mentioned endEntry because  
Transcript almost always does not display the last lines (they are  
buffered) and people get confused and believe that either their code or  
Squeak is wrong (but both is not the case).

> It is a very good suggestion Brian!

Indeed, and Briant's use of literal blocks in a literal Array is perfect  
(in the sense of: cannot be made better).

/Klaus

> Ron Teitelbaum