basic_syntax.io

# bare Prototypes begin with a Capital Letter, and you usually clone Object:
Cube := Object clone

# := creates a new 'slot' on the receiver and sets that slot to the value of the right-hand side:
Cube sides := 6

# Io has simple message-passing, no operator used: 'Receiver message'
Cube sides # ===> 6

# to def a method rather than a raw property, use the "method" message:
Cube description := method("A Plain Platonic Solid" print)

# methods are called just the same:
Cube description # => A Plain Platonic Solid

# 'inheritance' is via explicit clone.
D6 := Cube clone

# check properties and methods with "slotNames"...
D6 slotNames # => list(type) waitaminute!

# ...but method searching is done up the prototype chain, so there are no slotNames here, yet...
D6 sides # => 6

# to create an instance, use a lower-cased variable name when cloning
D6 description := method("A six-sided 3-D shape with pips on the sides")

fancy_d6 = D6 clone do(
  description := "A Gold-plated Wonder of a die"
)

# use "proto" to get the next object up the chain:
fancy_d6 proto proto # => Cube...

# use "perform" to send a Sequence (=String) as a message
fancy_d6 perform("sides") # is the same as d6 sides, but now we know how to metaprogram a bit!