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