Merge pull request #106 from fluentpython/main

lispy.py now runs in Python 3; dropped Python 2 support

py/lispy.py

@@ -4,9 +4,7 @@
 
 ################ Symbol, Procedure, classes
 
-from __future__ import division
-from __future__ import print_function
-import re, sys, StringIO
+import re, sys, io
 
 class Symbol(str): pass
 
@@ -21,7 +19,7 @@ _quote, _if, _set, _define, _lambda, _begin, _definemacro, = map(Sym,
 _quasiquote, _unquote, _unquotesplicing = map(Sym,
 "quasiquote   unquote   unquote-splicing".split())
 
-class Procedure(object):
+class Procedure:
     "A user-defined Scheme procedure."
     def __init__(self, parms, exp, env):
         self.parms, self.exp, self.env = parms, exp, env
@@ -33,12 +31,12 @@ class Procedure(object):
 def parse(inport):
     "Parse a program: read and expand/error-check it."
     # Backwards compatibility: given a str, convert it to an InPort
-    if isinstance(inport, str): inport = InPort(StringIO.StringIO(inport))
+    if isinstance(inport, str): inport = InPort(io.StringIO(inport))
     return expand(read(inport), toplevel=True)
 
 eof_object = Symbol('#<eof-object>') # Note: uninterned; can't be read
 
-class InPort(object):
+class InPort:
     "An input port. Retains a line of chars."
     tokenizer = r"""\s*(,@|[('`,)]|"(?:[\\].|[^\\"])*"|;.*|[^\s('"`,;)]*)(.*)"""
     def __init__(self, file):
@@ -83,7 +81,7 @@ def atom(token):
     'Numbers become numbers; #t and #f are booleans; "..." string; otherwise Symbol.'
     if token == '#t': return True
     elif token == '#f': return False
-    elif token[0] == '"': return token[1:-1].decode('string_escape')
+    elif token[0] == '"': return token[1:-1]
     try: return int(token)
     except ValueError:
         try: return float(token)
@@ -97,7 +95,7 @@ def to_string(x):
     if x is True: return "#t"
     elif x is False: return "#f"
     elif isa(x, Symbol): return x
-    elif isa(x, str): return '"%s"' % x.encode('string_escape').replace('"',r'\"')
+    elif isa(x, str): return repr(x)
     elif isa(x, list): return '('+' '.join(map(to_string, x))+')'
     elif isa(x, complex): return str(x).replace('j', 'i')
     else: return str(x)
@@ -158,7 +156,7 @@ def add_globals(self):
     self.update(vars(math))
     self.update(vars(cmath))
     self.update({
-     '+':op.add, '-':op.sub, '*':op.mul, '/':op.div, 'not':op.not_, 
+     '+':op.add, '-':op.sub, '*':op.mul, '/':op.truediv, 'not':op.not_,
      '>':op.gt, '<':op.lt, '>=':op.ge, '<=':op.le, '=':op.eq,
      'equal?':op.eq, 'eq?':op.is_, 'length':len, 'cons':cons,
      'car':lambda x:x[0], 'cdr':lambda x:x[1:], 'append':op.add,