3.8: Chapter Summary

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Page ID: 37619

Andrew P. Black, Stéphane Ducasse, Oscar Nierstrasz, Damien Pollet

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Squeak has (only) six reserved identifiers also called pseudo-variables: true, false, nil, self, super, and thisContext.
There are five kinds of literal objects: numbers (5, 2.5, 1.9e15, 2r111), characters ($a), strings ('hello'), symbols (#hello), and arrays (#('hello' #hello))
Strings are delimited by single quotes, comments by double quotes. To get a quote inside a string, double it.
Unlike strings, symbols are guaranteed to be globally unique.
Use #( ... ) to define a literal array. Use { ... } to define a dynamic array. Note that #(1+2) size $\rightarrow$ 3, but {1+2} size $\rightarrow$ 1
There are three kinds of messages: unary (e.g., 1 asString, Array new), binary (e.g., 3 + 4, 'hi', 'there'), and keyword (e.g., 'hi' at: 2 put: $o)
A cascaded message send is a sequence of messages sent to the same target, separated by semi-colons: OrderedCollection new add: #calvin; add: #hobbes; size $\rightarrow$ 2
Local variables are declared with vertical bars. Use := for assignment; $\leftarrow$ or _ will work as well but are deprecated since Squeak 3.9. |x| x:=1
Expressions consist of message sends, cascades and assignments, possibly grouped with parentheses. Statements are expressions separated by periods.
Block closures are expressions enclosed in square brackets. Blocks may take arguments and can contain temporary variables. The expressions in the block are not evaluated until you send the block a value... message with the correct number of arguments. [:x|x+2]value:4 $\rightarrow$ 6.
There is no dedicated syntax for control constructs, just messages that conditionally evaluate blocks. (Smalltalk includes: Class) ifTrue: [ Transcript show: Class superclass ]