For a change this is an exercism problem I know something about.

I did look at the exercism web site, and did all the SML exercises,

but could not find any for Smalltalk or Pharo.

The exercise is in fact about using a stack.

�� ��stack <- empty

�� ��for each character of the string

�� �� �� if it is one of ( [ { push it on the stack

�� �� �� if it is one of ) ] }

�� �� �� �� ��if the stack is empty or the top element does not

�� �� �� �� �� �� correspond to this character, return false

�� �� �� if it is not one of ( ) [ ] { } just ignore it

�� ��return (the stack is empty)

BOTH of the "return" constructs in this pseudo-code become

^ something

in Smalltalk.�� "Long returns", where "^" occurs inside a block,

are well defined, very useful, and universally accepted in Smalltalk.

There is no analogue of "^" for returning from a block.

By the way, this has nothing to do with #do:.�� It's about

returning from the method through any number of blocks.

For example, you will sometimes see code like

�� ��x := aDictionary at: aKey ifAbsent: [^false].

On Fri, 5 Apr 2019 at 00:16, Roelof Wobben <r.wobben@home.nl> wrote:

Hello,

For a challenge of Exercism I need to check if some parenthes and
brackets are balanced.

so for example

()�� = true
([])�� = true

but (])�� is not true because the bracket has no opening bracket.

Now I wonder if I can premature end a #do:�� like this

collection do: [:element | (condition with element) ifFalse: [^false]]

in pseudo code

is this a valid way to end the do ?
or is there a better way ?

Roelof