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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