Class: Subtle::Evaluator

Inherits:
Object
  • Object
show all
Defined in:
lib/subtle/evaluator.rb

Instance Method Summary collapse

Constructor Details

#initializeEvaluator

Returns a new instance of Evaluator.



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# File 'lib/subtle/evaluator.rb', line 3

def initialize
  @state = {}
  @parser    = Parser.new
  @transform = Transform.new
end

Instance Method Details

#ae!(tree, message = "") ⇒ Object



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# File 'lib/subtle/evaluator.rb', line 269

def ae!(tree, message = "")
  raise ArgumentError.new message << "\n" << tree.to_yaml
end

#eval(t) ⇒ Object



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# File 'lib/subtle/evaluator.rb', line 9

def eval(t)
  if String === t
    parsed = @parser.parse t
    t = @transform.apply parsed
  end

  if Hash === t
    type = t[:type]

    case type
    when :assignment
      @state[t[:identifier]] = try_eval t[:right]
    when :deassignment
      @state[t[:identifier]]
    when :function
      t[:function]
    when :function_call
      function = t[:function]
      adverb   = t[:adverb]
      right    = try_eval t[:right]
      if adverb
        case adverb
        when "/:"
          right = [right] unless Array === right
          right.map do |r|
            eval type: :function_call, function: function, right: r
          end
        else
          ae! t, "Invalid adverb #{adverb.inspect} for :function_call."
        end
      else
        _x = @state["x"]
        @state["x"] = right
        eval(function).tap do
          @state["x"] = _x
        end
      end
    when :variable_call
      identifier = t[:identifier]
      adverb     = t[:adverb]
      arguments  = t[:arguments]
      function = @state[identifier]
      eval type: :function_call, function: function, adverb: adverb,
        right: arguments
    when :monad
      verb   = t[:verb]
      adverb = t[:adverb]
      right  = try_eval t[:right]

      # `^` in Subtle is `**` in Ruby.
      verb = "**" if verb == "^"

      if adverb
        right = [right] unless Array === right
        case adverb
        when "//:"
          right.map do |r|
            eval type: :monad, verb: verb, adverb: "/", right: r
          end
        when "/"
          right.reduce do |fold, r|
            eval type: :dyad, verb: verb, left: fold, right: r
          end
        when "/:" # Map each over right
          right.map do |r|
            eval type: :monad, verb: verb, right: r
          end
        when "\\" # Scan
          [right.shift].tap do |scan|
            right.each do |r|
              scan << eval({type: :dyad, verb: verb, left: scan.last,
                            right: r})
            end
          end
        else
          ae! t, "Invalid adverb #{adverb} on Monads."
        end
      else
        if Array === right
          case verb
          when "&"
            [].tap do |ret|
              right.each_with_index do |r, i|
                r.times { ret << i }
              end
            end
          when "~"
            right.map do |r|
              r == 0 ? 1 : 0
            end
          when "+"
            if Array === right.first
              right.transpose
            else
              right
            end
          when "|"
            right.reverse
          end
        elsif Numeric === right
          case verb
          when "&"
            right.times.map { 0 }
          when "~"
            right == 0 ? 1 : 0
          when "+", "|"
            right
          end
        end
      end
    when :dyad
      # Evaluate right first.
      right  = try_eval t[:right]
      left   = try_eval t[:left]
      verb   = t[:verb]
      adverb = t[:adverb]

      # `^` in Subtle is `**` in Ruby,
      verb = "**" if verb == "^"
      # `=` is `==`,
      verb = "==" if verb == "="
      # `&` is `min` and `|` is `max.
      verb = "min" if verb == "&"
      verb = "max" if verb == "|"

      if adverb
        case adverb
        when "/:" # Map each over right
          right.map do |r|
            eval type: :dyad, left: left, verb: verb, right: r
          end
        when "\\:" # Map each over left
          left.map do |l|
            eval type: :dyad, left: l, verb: verb, right: right
          end
        else
          ae! t, "Invalid Adverb #{adverb}"
        end
      else
        case verb
        when "+", "-", "*", "/", "%", "**", "==", "<", ">"
          if Numeric === left && Numeric === right
            ret = left.send(verb, right)
            if %w{== < >}.include?(verb)
              ret ? 1 : 0
            else
              ret
            end
          elsif Array === left && Array === right
            if left.size != right.size
              ae! t, "Size of left array must be the same as the size of" +
                " right one, but #{left.size} != #{right.size}."
            end

            left.zip(right).map do |l, r|
              if Array === l || Array === r
                eval type: :dyad, verb: verb, left: l, right: r
              else
                ret = (try_eval l).send(verb, try_eval(r))
                if %w{== < >}.include?(verb)
                  ret ? 1 : 0
                else
                  ret
                end
              end
            end
          elsif Array === left && Numeric === right
            left.map do |l|
              # Multi-dimensional arrays
              if Array === l
                eval type: :dyad, verb: verb, left: l, right: right
              else
                ret = (try_eval l).send(verb, right)
                if %w{== < >}.include?(verb)
                  ret ? 1 : 0
                else
                  ret
                end
              end
            end
          elsif Numeric === left && Array === right
            right.map do |r|
              # Multi-dimensional arrays
              if Array === r
                eval type: :dyad, verb: verb, left: left, right: r
              else
                ret = left.send(verb, r)
                if %w{== < >}.include?(verb)
                  ret ? 1 : 0
                else
                  ret
                end
              end
            end
          else
            ae! t, "Left and Array must be Numeric or Arrays." +
              " You passed in #{left.class} and #{right.class}."
          end
        when "max", "min"
          if Numeric === left && Numeric === right
            [left, right].send(verb)
          elsif Array === left && Array === right
            if left.size != right.size
              ae! t, "Size of left array must be the same as the size of" +
                " right one, but #{left.size} != #{right.size}."
            end
            left.zip(right).map do |l, r|
              eval type: :dyad, verb: verb, left: l, right: r
            end
          elsif Array === left && Numeric === right
            left.map do |l|
              if Array === l
                eval type: :dyad, verb: verb, left: l, right: right
              else
                [l, right].send(verb)
              end
            end
          elsif Numeric === left && Array === right
            right.map do |r|
              if Array === r
                eval type: :dyad, verb: verb, left: left, right: r
              else
                [left, r].send(verb)
              end
            end
          else
            ae! t
          end
        when "!"
          if Numeric === left && Array === right
            right.rotate(left)
          else
            ae! t, "Left must be Numeric and right must be an Array for" +
              " rotate (`!`) dyad. You passed in #{left.class} and" +
              " #{right.class}"
          end
        else
          ae! t, "Invalid verb #{verb}."
        end
      end
    when :enumerate
      last = try_eval t[:last]
      if Numeric === last
        (0...last.floor).to_a
      else
        ae! t, "`last` must be Numeric for type: :enumerate. You passed" +
          " in #{last.class}."
      end
    else
      ae! t, "Type #{t[:type].inspect} not implemented."
    end
  else
    t
  end
end

#try_eval(t) ⇒ Object



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# File 'lib/subtle/evaluator.rb', line 265

def try_eval(t)
  Hash === t ? eval(t) : t
end