Quoting constructs: Difference between revisions

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<lang smalltalk>aBlock value. "evaluate the block, passing no argument"

anotherBlock value:1 value:2. "evaluate the block, passing two arguments"</lang>

The most basic implementation of such a control structure is found in the Boolean subclasses True and False, which implement eg. "ifTrue:arg" and "ifFalse:". Here are those two as concrete example:

The most basic implementation of such a control structure is found in the Boolean subclasses True and False, which implement eg. "<tt>ifTrue:arg</tt>" and "<tt>ifFalse:</tt>". Here are those two as concrete example:

<lang smalltalk>in the True class:

ifTrue: aBlock

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ifTrue: aBlock

^ nil "I am false, so I ignore the block"</lang>

Thus, the expression "someBoolean ifTrue:[ 'hello print' ]" will either evaluate the lambda or not, depending on the someBoolean receiver.

Thus, the expression <tt>"someBoolean ifTrue:[ 'hello print' ]"</tt> will either evaluate the lambda or not, depending on the someBoolean receiver.

Obviously, you can teach other objects on how to respond to "value" messages and then use them as if they where blocks.

Actually, the Object class also implements "value", so you can also write:

<~~lang smalltalk~~>a := someCondition ifTrue:10 ifFalse:20</~~lang~~>

"<tt>a := someCondition ifTrue:10 ifFalse:20</tt>".

~~which~~ works because "Object value" simply returns the receiver.

Thich works because "<tt>Object value</tt>" simply returns the receiver.

In addition, some Smalltalk dialects implement additional syntax extensions.