When I teach Smalltalk, this is one of the most beautiful exercises for
students.
Those who get it will love Smalltalk, those who don't often leave the
project soon ;-)
BTW: This is not a visitor or any other pattern, it really is just
Polymorphism at work and the reason why back in the 90ies, people said
if statements should be replaced by Polymorphism
Joachim
Am 31.10.16 um 14:17 schrieb CodeDmitry:
I am looking at
ifTrue: alternativeBlock
"If the receiver is false (i.e., the condition is false), then the
value is
the
false alternative, which is nil. Otherwise answer the result of
evaluating
the argument, alternativeBlock. Create an error notification if the
receiver is nonBoolean. Execution does not actually reach here because
the expression is compiled in-line."
self subclassResponsibility
In order to perform the block, ifTrue must somehow end up evaluating the
block, but this code only sends a subclassResponsibility message to itself
and implicitly returns itself.
Where does the block actually get evaluated?
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