On Sun, Nov 28, 2010 at 1:37 PM, James Ladd <james_ladd@hotmail.com> wrote:

Hi All,

I'm wondering about documentation to describe the block semantics of Pharo Smalltalk,
Specifically around the return context when a block contains a return:� [ ^ foo ]

Is a block valid only within the method that defined it and passed / called it?
I think it is, and when called outside of the context there is a BlockContext no longer exists error.

Note that BlockContext is no longer used. �| b | b := [thisContext class]. �{ b class. b value } answers { BlockClosure. MethodContext }.

The block is valid, but the attempt to return from a method can only be made once, whether made form an embedded block or the mehtod itself. �So the first attempt to retur wins. �However, a block =containing a return can still be evaluated. �An error will occur only if the retrn is actually executed.

So e.g.

�� fibBlock

�� | b |

�� ^b := [:n| n < 0 ifTrue: [^self error: 'Nooooooo!']. �n < 2 ifTrue: [1] ifFalse: [(b value: n - 1) + (b value: n - 2)]]

�� (0 to: 10) collect: self fibBlock

works fine but

�� self fibBlock value: -1

will produce a cannot return error.

However, I'm looking for documentation or confirmation to ensure my testing was correct.

Rgs, James.