break out of do

Is there a way to break out of a do:? For example, if I use do: to  
iterate through the characters in a string and I find a character I  
don't want to allow, can I break out and avoid examining the remaining  
characters?

---
Mark Volkmann




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>>>>> "Mark" == Mark Volkmann <[hidden email]> writes:

Mark> Is there a way to break out of a do:? For example, if I use do: to
Mark> iterate through the characters in a string and I find a character I
Mark> don't want to allow, can I break out and avoid examining the remaining
Mark> characters?

The simplest way is to factor your code such that when you are done processing
in your loop, you answer from the method when you've reached that.

    contains: anItem

    self do: [:each|
      "some stuff here if you want"
      anItem = each ifTrue: [^true]. "breaks the loop, returns true to caller"
      "some more stuff here if you want"
    ].
    ^false "default answer if not found"
 
I'd suggest trying to get your code shaped like that.  It'll be the
most familar.

There are more complicated ways to do it with exceptions if you need
to stay within the same method.  Don't do that. :)

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<[hidden email]> <URL:http://www.stonehenge.com/merlyn/>
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On Friday 03 Oct 2008 6:34:24 pm Mark Volkmann wrote:
> Is there a way to break out of a do:? For example, if I use do: to
> iterate through the characters in a string and I find a character I
> don't want to allow, can I break out and avoid examining the remaining
> characters?
A string is a collection and there are a rich set of methods for iterating
over a collection. Bring up method search tool (ALT+Shift+W or
WorldMenu->windows->find message names) and enter "includes" you will find
methods like includes:, includesAnyOf:, includesAllOf:, anySatisfy: and so
on.

The Method search tool is a really nifty tool for searching out methods.

Subbu
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Randal L. Schwartz <merlyn <at> stonehenge.com> writes:

>
> snip...
>
> There are more complicated ways to do it with exceptions if you need
> to stay within the same method.  Don't do that. :)
>

For the fun of it, see also

http://article.gmane.org/gmane.comp.lang.smalltalk.gnu.general/3375/match=break



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>>>>> "Nicolas" == Nicolas Cellier <[hidden email]> writes:

Nicolas> For the fun of it, see also

Nicolas> http://article.gmane.org/gmane.comp.lang.smalltalk.gnu.general/3375/match=break

Oww.  I remember that.  It makes my head hurt.

You could even go further:

    Object >> valuedEscaper: aBlock
       ^ aBlock value: [ :finalValue | ^finalValue ]

    ...

    found := self valuedEscaper: [:escape |
           1 to: 10 do: [ :x |
               x = 3 ifTrue: [escape value: true].
           ]
    false].

Oh geez.  I think I just reinvented continuations. :)

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Am 03.10.2008 um 09:27 schrieb Randal L. Schwartz:



That would be a perfect opportunity to employ  
#valueWithPossibleArgument:.

- Bert -


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>>>>> "Bert" == Bert Freudenberg <[hidden email]> writes:

Bert> That would be a perfect opportunity to employ  #valueWithPossibleArgument:.

And with this, the newbies heads have exploded. :)

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Am 03.10.2008 um 11:02 schrieb Randal L. Schwartz:

>>>>>> "Bert" == Bert Freudenberg <[hidden email]> writes:
>
> Bert> That would be a perfect opportunity to employ  
> #valueWithPossibleArgument:.
>
> And with this, the newbies heads have exploded. :)

Hehe :) If they followed the thread closely they will have noticed  
that this is a tangent, the original recommendation was to factor this  
out into a separate method and use a local return. And that's still  
the way you should do it.

Something to take away would be that Squeak lets you implement the  
control structures you need rather easily, which is great once you  
need it.

- Bert -


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