Class: Fusion::Interpreter::Thunk

Inherits:
Object
  • Object
show all
Defined in:
lib/fusion/interpreter/thunk.rb

Defined Under Namespace

Classes: ReadFailure

Instance Method Summary collapse

Constructor Details

#initialize(&compute) ⇒ Thunk

Returns a new instance of Thunk.



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# File 'lib/fusion/interpreter/thunk.rb', line 16

def initialize(&compute)
  @compute = compute
  @state = :unforced # :unforced | :forcing | :done
  @value = nil # memoized result: runtime value/error | ReadFailure
end

Instance Method Details

#force(operation: "loading code", input: NULL, site: { origin: "code", file: nil }) ⇒ Object

operation/input/site describe the @-reference forcing this thunk. They are NOT passed to @compute, because they differ when evaluating the same Thunk for different @-references. They MUST NOT become part or the memoized value.



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# File 'lib/fusion/interpreter/thunk.rb', line 25

def force(operation: "loading code", input: NULL, site: { origin: "code", file: nil })
  result = case @state
  when :done
    @value
  when :forcing
    # Re-entering while still computing results in a non-productive data cycle. Not memoized.
    ErrorVal.from_runtime(kind: "reference_error", **site, operation: operation, input: input, message: "non-productive data cycle")
  when :unforced
    @state = :forcing
    begin
      @value = @compute.call
    rescue ReadFailure => failure
      # Memoize the Ruby error itself. Turn it into a Fusion runtime error below.
      @value = failure
    end
    @state = :done
    @value
  end

  case result
  when ReadFailure
    ErrorVal.from_runtime(kind: "reference_error", **site, operation: operation, input: input, message: result.message)
  else
    result
  end
end