Expressions and Messages

All the statements will contain one, or more expressions.

There are no native operators, and all expressions are either mentions of an object, or messages sent to them.

Messages

There are three different semantics for messages

  • Unary Messages -- These are more than one unicode code point long, and take no parameters, and have no colon after them.

  • Binary Messages -- These are either exactly one unicode code point long, or are equal to:: , or are composed of any of =+-*&%$@~<>?;. these take a single argument.

  • Keyword Messages -- These are arbitrarily long names, separated by colons

Examples for each follow:

  • Unary: 2 sin or 2 toString or 'test' reverse
  • Binary: 2 + 3 or True | False or 'te%st' % ['s']
  • Keyword: 2 between: 0 and: 3 or True either: blk0 or: blk1 or Array join: ', '

Basic messages for the Number objects

  • Binary +

    • Adds something to a number
      • Normally operates on Strings and Numbers
    • 3 + 5 gives 8. 3 + 'test' gives '3test'
      • Note that in no possible scenario a string would be implicitly cast to a number.

  • Binary -

    • Subtracts a number from another
    • 10 - 8 gives 2

  • Binary *

    • Multiplies a number by another
    • 2 * 3 gives 6

  • Keyword pow:

    • raises a number to a numeric power
    • 2 pow: 3 gives 8

Tip:
To see all the Number methods, type :!m Number in the interactive interpreter

Comparing two numbers

The method names are >, <, >=:, <=:, =, !=:

equality can be tested with the alias method equals:, However, when overriding equality, only = must be overridden.

Shortcuts for number manipulations

The methods +=:, *=:, -=:, /=: exist, but they change the object itself, so any instance of that object will have a different value.

var a is 123.
var b is a.

a -=: 3.

Pen writeln: b. #Prints 120

Evaluation Order

The generic order of evaluation is

  1. The receiver
  2. The first argument (if present)
  3. The second argument (if present)
  4. and so on

Parens are treated normally.