Initial move of code from git repo.

2018-04-14 18:13:13 -07:00
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+# -*- coding: utf-8 -*-
+'''
+
+
+A dialect of Joy in Python.
+
+
+Joy is a programming language created by Manfred von Thun that is easy to
+use and understand and has many other nice properties.  This Python script
+is an interpreter for a dialect of Joy that attempts to stay very close
+to the spirit of Joy but does not precisely match the behaviour of the
+original version(s) written in C.  A Tkinter GUI is provided as well.
+
+
+    Copyright © 2014, 2016, 2017 Simon Forman
+
+    This file is part of Joypy.
+
+    Joypy is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    Joypy is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with Joypy.  If not see <http://www.gnu.org/licenses/>.
+
+
+§ joy()
+
+The basic joy() function is quite straightforward.  It iterates through a
+sequence of terms which are either literals (strings, numbers, sequences)
+or functions.  Literals are put onto the stack and functions are
+executed.
+
+Every Joy function is an unary mapping from stacks to stacks.  Even
+literals are considered to be functions that accept a stack and return a
+new stack with the literal value on top.
+
+Exports:
+
+  joy(stack, expression, dictionary, viewer=None)
+
+  run(text, stack, dictionary, viewer=None)
+
+  repl(stack=(), dictionary=())
+
+'''
+from __future__ import print_function
+try:
+  input = raw_input
+except NameError:
+  pass
+from traceback import print_exc, format_exc
+from .parser import text_to_expression, ParseError, Symbol
+from .utils.stack import stack_to_string
+from .utils.pretty_print import TracePrinter
+
+
+def joy(stack, expression, dictionary, viewer=None):
+  '''
+  Evaluate the Joy expression on the stack.
+  '''
+  while expression:
+
+    if viewer: viewer(stack, expression)
+
+    term, expression = expression
+    if isinstance(term, Symbol):
+      term = dictionary[term]
+      stack, expression, dictionary = term(stack, expression, dictionary)
+    else:
+      stack = term, stack
+
+  if viewer: viewer(stack, expression)
+  return stack, expression, dictionary
+
+
+def run(text, stack, dictionary, viewer=None):
+  '''
+  Return the stack resulting from running the Joy code text on the stack.
+  '''
+  expression = text_to_expression(text)
+  return joy(stack, expression, dictionary, viewer)
+
+
+def repl(stack=(), dictionary=None):
+  '''
+  Read-Evaluate-Print Loop
+
+  Accept input and run it on the stack, loop.
+  '''
+  if dictionary is None:
+    dictionary = {}
+  try:
+    while True:
+      print()
+      print(stack_to_string(stack), '<-top')
+      print()
+      try:
+        text = input('joy? ')
+      except (EOFError, KeyboardInterrupt):
+        break
+      viewer = TracePrinter()
+      try:
+        stack, _, dictionary = run(text, stack, dictionary, viewer.viewer)
+      except:
+        exc = format_exc() # Capture the exception.
+        viewer.print_() # Print the Joy trace.
+        print('-' * 73)
+        print(exc) # Print the original exception.
+      else:
+        viewer.print_()
+  except:
+    print_exc()
+  print()
+  return stack