parameters

parameterization.atomo.hs

Parameter = Object clone
Parameter new: v := Parameter clone do: {
    value: (self) = v
    value: _ = v
}

(p: Parameter) _? := p value: self

(p: Parameter) set: v :=
    (p) value: (self) = v

with: (p: Parameter) as: new do: (action: Block) := {
    old = p _?
    p set: new
    p ensuring: @(set: old) do: action
} call

Example:

x = Parameter new: 0
foo := bar
bar := x _? print
foo
  => 0
with: x as: 1 do: { foo }
  => 1

And it's thread-safe!

x = Parameter new: 0
{ Timer sleep: 5 seconds; x _? print } spawn
x set: 42
x _? print
  => 42 is the value here
  => 0 is printed by the other process after 5 seconds