gmane.comp.lang.smalltalk.squeak.beginners

How to put a block into an Array

Newbie here, working my way through Guzdial's Squeak: Object-Oriented
Design with Multimedia Applications (2001). One of the exercises
requires building an Array with a block of code as an element, the
idea is to lookup the stored block in some way and execute it. But,
how do you store a block of code in an Array?

For example, I can do this:

[Transcript show: 'a message'] value

But I can't get this to work:

myArray := #([Transcript show: 'a message']).
(myArray at: 1) value

The reason is that (myArray at: 1) doesn't recognize the stored object
as a block. Inspecting it shows the odd symbol: #[ ??

Can someone get me back on the clue train?

Thanks,

David

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Matthew Fulmer | 16 May 21:17

Re: How to put a block into an Array

On Fri, May 16, 2008 at 12:11:50PM -0700, David Finlayson wrote:
> Newbie here, working my way through Guzdial's Squeak: Object-Oriented
> Design with Multimedia Applications (2001). One of the exercises
> requires building an Array with a block of code as an element, the
> idea is to lookup the stored block in some way and execute it. But,
> how do you store a block of code in an Array?
> 
> For example, I can do this:
> 
> [Transcript show: 'a message'] value
> 
> But I can't get this to work:
> 
> myArray := #([Transcript show: 'a message']).
> (myArray at: 1) value
> 
> The reason is that (myArray at: 1) doesn't recognize the stored object
> as a block. Inspecting it shows the odd symbol: #[ ??
> 
> Can someone get me back on the clue train?

the #() syntax only supports numbers and symbols. Use the brace
syntax, or build the array using messages:

myArray := {[Transcript show: 'a message']}
myArray := Array with: [Transcript show: 'a message']

--

-- 
Matthew Fulmer -- http://mtfulmer.wordpress.com/

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David Finlayson | 16 May 22:02

Re: How to put a block into an Array

Thanks, that did it. There is a nice explaination of this syntax here:

http://www.smalltalk.org/articles/article_20040920_a2.html

which I was not aware of. My Smalltalk books are dated and don't have
the Squeak extensions to the language.

David

On Fri, May 16, 2008 at 12:17 PM, Matthew Fulmer <tapplek <at> gmail.com> wrote:
> On Fri, May 16, 2008 at 12:11:50PM -0700, David Finlayson wrote:
>> Newbie here, working my way through Guzdial's Squeak: Object-Oriented
>> Design with Multimedia Applications (2001). One of the exercises
>> requires building an Array with a block of code as an element, the
>> idea is to lookup the stored block in some way and execute it. But,
>> how do you store a block of code in an Array?
>>
>> For example, I can do this:
>>
>> [Transcript show: 'a message'] value
>>
>> But I can't get this to work:
>>
>> myArray := #([Transcript show: 'a message']).
>> (myArray at: 1) value
>>
>> The reason is that (myArray at: 1) doesn't recognize the stored object
>> as a block. Inspecting it shows the odd symbol: #[ ??
>>
>> Can someone get me back on the clue train?

(Continue reading)

headers

Matthew Fulmer | 16 May 22:10

Re: How to put a block into an Array

On Fri, May 16, 2008 at 01:02:03PM -0700, David Finlayson wrote:
> Thanks, that did it. There is a nice explaination of this syntax here:
> 
> http://www.smalltalk.org/articles/article_20040920_a2.html
> 
> which I was not aware of. My Smalltalk books are dated and don't have
> the Squeak extensions to the language.

There are three good syntax guides at
http://squeak.org/Documentation

--

-- 
Matthew Fulmer -- http://mtfulmer.wordpress.com/