Introduction Terminology Expressions Control Objects Inheritance Technology Summary

Control

Smalltalk has no control structures except message passing. However, familiar control structures are defined as methods on booleans and integers. See slide sm-control.

Keyword methods

    (i <= 7) 
          ifTrue: [ m:= "oke" ]
          ifFalse: [ ... ]

Control structures

conditional -- ifTrue: ifFalse:
iteration -- whileTrue:
looping -- to: by: do: [ :i | ... ]

slide: Smalltalk -- control

For example, an if-statement may be obtained by defining the method ifTrue: ifFalse: on booleans. (Despite the use of keywords, parameter passing in Smalltalk is positional. Each sequence of keywords may be regarded as a different method.) In a similar vein, we may define iteration and looping. For looping, we may employ the parameter mechanism of blocks, as indicated above.