Add the grass interpreter

vendor/README

@@ -34,6 +34,11 @@ Befunge: cfunge-0.9.0.tar.bz2
   * http://sourceforge.net/projects/cfunge/
   * License: GPL3
 
+Grass: grass.rb
+  * http://www.blue.sky.or.jp/grass/
+  * License: BSD 2-Clause
+  * slightly modified for Ruby 2+
+
 LOLCODE: lci-0.10.5.zip
   * http://lolcode.org/
   * License: GPL3+

vendor/grass.rb

@@ -0,0 +1,204 @@
+#!/usr/bin/ruby -Ku
+#
+# grass.rb - Grass interpreter
+# http://www.blue.sky.or.jp/grass/
+#
+# Copyright (C) 2006, 2007 UENO Katsuhiro. All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+# 1. Redistributions of source code must retain the above copyright
+#    notice, this list of conditions and the following disclaimer.
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions and the following disclaimer in
+#    the documentation and/or other materials provided with the
+#    distribution.
+#
+# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS''
+# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+# THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+# PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS
+# BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
+# BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+# WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
+# OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
+# IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#
+# History:
+#
+# 2007-10-02
+#   - Follow the latest changes of the definition of Grass.
+# 2007-09-20
+#   - First version.
+#
+
+require 'pp'
+
+class Grass
+
+  RELEASE_DATE = '2007-10-02'
+
+  class Error < StandardError ; end
+  class RuntimeError < Error ; end
+  class IllegalState < Error ; end
+
+  Machine = Struct.new(:code, :env, :dump)
+
+  class Value
+    def char_code
+      raise RuntimeError, "not a char"
+    end
+
+    def app(m, arg)
+      raise RuntimeError, "app undefined"
+    end
+  end
+
+  class Insn
+  end
+
+  class App < Insn
+    def initialize(m, n)
+      @m, @n = m, n
+    end
+
+    def eval(m)
+      f, v = m.env[-@m], m.env[-@n]
+      raise "out of bound" unless f and v
+      f.app m, v
+    end
+
+    def pretty_print(q)
+      q.text 'App'
+      q.group(4, '(', ')') { q.seplist([@m,@n]) { |i| q.text "#{i}" } }
+    end
+    alias inspect pretty_print_inspect
+  end
+
+  class Abs < Insn
+    def initialize(body)
+      @body = body
+    end
+
+    def eval(m)
+      m.env.push Fn.new(@body, m.env.dup)
+    end
+
+    def pretty_print(q)
+      q.text 'Abs'
+      q.group(4, '(', ')') { @body.pretty_print(q) }
+    end
+    alias inspect pretty_print_inspect
+  end
+
+  class Fn < Value
+    def initialize(code, env)
+      @code, @env = code, env
+    end
+
+    def app(m, arg)
+      m.dump.push [m.code, m.env]
+      m.code, m.env = @code.dup, @env.dup
+      m.env.push arg
+    end
+  end
+
+  ChurchTrue  = Fn.new([Abs.new([App.new(3,2)])], [Fn.new([],[])])
+  ChurchFalse = Fn.new([Abs.new([])], [])
+
+  class CharFn < Value
+    def initialize(char_code)
+      @char_code = char_code
+    end
+    attr_reader :char_code
+
+    def app(m, arg)
+      ret = @char_code == arg.char_code ? ChurchTrue : ChurchFalse
+      m.env.push ret
+    end
+  end
+
+  class Succ < Value
+    def app(m, arg)
+      m.env.push CharFn.new((arg.char_code + 1) & 255)
+    end
+  end
+
+  class Out < Value
+    def app(m, arg)
+      $stdout.print arg.char_code.chr
+      $stdout.flush
+      m.env.push arg
+    end
+  end
+
+  class In < Value
+    def app(m, arg)
+      ch = $stdin.getc
+      ret = ch ? CharFn.new(ch) : arg
+      m.env.push ret
+    end
+  end
+
+  private
+
+  def eval(m)
+    while true
+      insn = m.code.shift
+      if insn then
+        insn.eval m
+      else
+        break if m.dump.empty?
+        ret = m.env.last
+        raise IllegalState, "no return value" unless ret
+        m.code, m.env = m.dump.pop
+        m.env.push ret
+      end
+    end
+    raise IllegalState, "illegal final machine state" unless m.env.size == 1
+    m.env.first
+  end
+
+  InitialEnv = [In.new, CharFn.new(?w.ord), Succ.new, Out.new]
+  InitialDump = [[[], []], [[App.new(1, 1)], []]]
+
+  def start(code)
+    eval Machine.new(code, InitialEnv, InitialDump)
+  end
+
+  def parse(src)
+    code = []
+    src = src.sub(/\A[^wｗ]*/, '').gsub(/[^wｗWＷvｖ]/, '')
+    src.split(/[vｖ]+/).each { |s|
+      a = s.scan(/[wｗ]+|[WＷ]+/).map { |i| i.split(//).size }
+      arity = 0
+      arity = a.shift if /\A[wｗ]/ =~ s
+      raise "parse error at app" unless a.size % 2 == 0
+      body = []
+      0.step(a.size - 1, 2) { |i| body.push App.new(a[i], a[i+1]) }
+      insn = (0...arity).inject(body) { |body,| [Abs.new(body)] }
+      code.concat insn
+    }
+    code
+  end
+
+  public
+
+  def run(src)
+    start parse(src)
+  end
+
+end
+
+if $0 == __FILE__ then
+  $stderr.puts "Grass #{Grass::RELEASE_DATE}" if $VERBOSE
+  Grass.new.run $<.read
+end
+
+
+# Local Variables:
+# coding: utf-8
+# End: