Editing Self (programming language) (section)

=== Basic syntax ===
The syntax for accessing slots is similar to that of Smalltalk. Three kinds of messages are available:
;unary : <code>''receiver'' slot_name</code>
;binary : <code>''receiver'' + ''argument''</code>
;keyword : <code>''receiver'' keyword: ''arg1'' With: ''arg2''</code>

All messages return results, so the receiver (if present) and arguments can be themselves the result of other messages. Following a message by a period means Self will discard the returned value. For example:

<syntaxhighlight lang="smalltalk">'Hello, World!' print.</syntaxhighlight>

This is the Self version of the [["Hello, World!" program]]. The <code>'</code> syntax indicates a literal string object. Other literals include numbers, blocks and general objects.

Grouping can be forced by using parentheses. In the absence of explicit grouping, the unary messages are considered to have the highest precedence followed by binary (grouping left to right) and the keywords having the lowest. The use of keywords for assignment would lead to some extra parenthesis where expressions also had keyword messages, so to avoid that Self requires that the first part of a keyword message selector start with a lowercase letter, and subsequent parts start with an uppercase letter.

<syntaxhighlight lang="smalltalk">valid: base bottom
          between: ligature bottom + height
          And: base top / scale factor.</syntaxhighlight>

can be parsed unambiguously, and means the same as:

<syntaxhighlight lang="smalltalk">valid: ((base bottom)
            between: ((ligature bottom) + height)
            And: ((base top) / (scale factor))).</syntaxhighlight>

In Smalltalk-80, the same expression would be written as:

<syntaxhighlight lang="smalltalk">valid := self base bottom
             between: self ligature bottom + self height
             and: self base top / self scale factor.</syntaxhighlight>

assuming <code>base</code>, <code>ligature</code>, <code>height</code> and <code>scale</code> were not [[instance variable]]s of <code>self</code> but were, in fact, methods.