def testTrampoline(self):
# trampolined factorial
def fact(n, ans, cont):
if n < 2:
return bounce(cont, ans)
else:
return bounce(fact, n-1, n*ans, cont)
ans = pogo_stick(bounce(fact, 5, 1, lambda d:d))
self.assertEqual(ans, 120)
ans = pogo_stick(bounce(fact, 1, 1, lambda d:d))
self.assertEqual(ans, 1)
# member search
def memq(target, lst, cont):
if lst == []:
return bounce(cont, False)
elif target == lst[0]:
return bounce(cont, True)
else:
return bounce(memq, target, lst[1:], cont)
ans = pogo_stick(bounce(memq, 3, [1, 2, 3, 4, 5], lambda d:d))
self.assertEqual(ans, True)
ans = pogo_stick(bounce(memq, 3, [1, 2, 4, 5, 6], lambda d:d))
self.assertEqual(ans, False)
def parse_sexp(self, tokens, cont):
"""Parse a single S-expression.
"""
token_type = tokens[0][1]
if token_type in (TOKEN_TYPE_BOOLEAN,
TOKEN_TYPE_INTEGER,
TOKEN_TYPE_FLOAT,
TOKEN_TYPE_FRACTION,
TOKEN_TYPE_COMPLEX,
TOKEN_TYPE_STRING,
TOKEN_TYPE_SYMBOL,):
return bounce(self.parse_lexeme_datum, tokens, cont)
elif token_type == TOKEN_TYPE_SINGLE_QUOTE:
def make_quote(word):
return bounce(cont, lib_list(tsym('quote'), word))
self.consume(tokens, TOKEN_TYPE_SINGLE_QUOTE)
return bounce(self.parse_sexp, tokens, make_quote)
elif token_type == TOKEN_TYPE_LPAREN:
return bounce(self.parse_list, tokens, cont)
else:
raise SchemeError('bad expression syntax')
def memq(target, lst, cont):
if lst == []:
return bounce(cont, False)
elif target == lst[0]:
return bounce(cont, True)
else:
return bounce(memq, target, lst[1:], cont)
def done_rest(rest):
if rest[0] == '(':
if rest[1:-1] == '':
return bounce(cont, '(' + first + ')')
else:
return bounce(cont, '(' + first + ' ' + rest[1:-1] + ')')
else:
return bounce(cont, '(' + first + ' . ' + rest + ')')
def _to_python_list(scmlist, pylist, cont):
"""Convert a Scheme list into a Python list.
"""
def got_first(first):
nonlocal pylist
pylist.append(first)
return bounce(_to_python_list, scmlist[1], pylist, cont)
if scmlist.isnil:
return bounce(cont, pylist)
if isinstance(scmlist[0], Pair):
return bounce(_to_python_list, scmlist[0], [], got_first)
pylist.append(scmlist[0])
return bounce(_to_python_list, scmlist[1], pylist, cont)
def _from_python_list(pylist, scmlist, cont):
"""Produce a Scheme list from a Python list.
"""
def got_first(first):
nonlocal scmlist
scmlist = Pair([first, scmlist])
return bounce(_from_python_list, pylist[1:], scmlist, cont)
if pylist == []:
return bounce(cont, scmlist)
if isinstance(pylist[0], list):
return bounce(_from_python_list, list(reversed(pylist[0])), NIL, got_first)
scmlist = Pair([pylist[0], scmlist])
return bounce(_from_python_list, pylist[1:], scmlist, cont)
def parse_list(self, tokens, cont):
"""Parse a Scheme list.
"""
def done_rest(rest):
self.consume(tokens, TOKEN_TYPE_RPAREN)
return bounce(cont, rest)
self.consume(tokens, TOKEN_TYPE_LPAREN)
return bounce(self.parse_rest_sexps, tokens, done_rest)
def parse(self, tokens):
"""The interface. Returns the list of S-expressions
generated from the given token list.
"""
self.sexps = []
while True:
if len(tokens) == 0:
return self.sexps
self.sexps.append(pogo_stick(bounce(self.parse_sexp, tokens, lambda d:d)))
def done_first(first):
def done_rest(rest):
if rest[0] == '(':
if rest[1:-1] == '':
return bounce(cont, '(' + first + ')')
else:
return bounce(cont, '(' + first + ' ' + rest[1:-1] + ')')
else:
return bounce(cont, '(' + first + ' . ' + rest + ')')
return bounce(_to_str, p[1], done_rest)
def _to_str(p, cont):
"""Give the neat string representation of a pair.
"""
def done_first(first):
def done_rest(rest):
if rest[0] == '(':
if rest[1:-1] == '':
return bounce(cont, '(' + first + ')')
else:
return bounce(cont, '(' + first + ' ' + rest[1:-1] + ')')
else:
return bounce(cont, '(' + first + ' . ' + rest + ')')
return bounce(_to_str, p[1], done_rest)
if not isinstance(p, Pair):
return bounce(cont, str(p))
if p.isnil:
return bounce(cont, '()')
return bounce(_to_str, p[0], done_first)
def parse_rest_sexps(self, tokens, cont):
"""Parse the S-expressions in the list. The list may
be a Scheme list or a dotted partial list.
"""
token_type = tokens[0][1]
if token_type == TOKEN_TYPE_DOT:
self.consume(tokens, TOKEN_TYPE_DOT)
return bounce(self.parse_sexp, tokens, cont)
elif token_type != TOKEN_TYPE_RPAREN:
def done_first(first):
nonlocal saved_first_exp
saved_first_exp = first
return bounce(self.parse_rest_sexps, tokens, done_rest)
def done_rest(rest):
return bounce(cont, cons(saved_first_exp, rest))
saved_first_exp = None
return bounce(self.parse_sexp, tokens, done_first)
else:
return bounce(cont, NIL)
def parse_lexeme_datum(self, tokens, cont):
token = tokens[0]
token_type = token[1]
if token_type == TOKEN_TYPE_BOOLEAN:
self.consume(tokens, TOKEN_TYPE_BOOLEAN)
if token[0] == '#t':
return bounce(cont, True)
else:
return bounce(cont, False)
elif token_type == TOKEN_TYPE_STRING:
self.consume(tokens, TOKEN_TYPE_STRING)
return bounce(cont, token[0][1:-1])
elif token_type == TOKEN_TYPE_SYMBOL:
self.consume(tokens, TOKEN_TYPE_SYMBOL)
return bounce(cont, tsym(token[0]))
elif token_type == TOKEN_TYPE_INTEGER:
self.consume(tokens, TOKEN_TYPE_INTEGER)
return bounce(cont, int(token[0]))
elif token_type == TOKEN_TYPE_FLOAT:
self.consume(tokens, TOKEN_TYPE_FLOAT)
return bounce(cont, float(token[0]))
elif token_type == TOKEN_TYPE_FRACTION:
self.consume(tokens, TOKEN_TYPE_FRACTION)
numer, denom = token[0].split('/')
return bounce(cont, float(numer) / float(denom))
elif token_type == TOKEN_TYPE_COMPLEX:
self.consume(tokens, TOKEN_TYPE_COMPLEX)
return bounce(cont, complex(token[0].replace('i', 'j')))
else:
raise SchemeError(token, 'is not a lexeme datum')
def fact(n, ans, cont):
if n < 2:
return bounce(cont, ans)
else:
return bounce(fact, n-1, n*ans, cont)
def done_first(first):
nonlocal saved_first_exp
saved_first_exp = first
return bounce(self.parse_rest_sexps, tokens, done_rest)
def got_first(first):
nonlocal scmlist
scmlist = Pair([first, scmlist])
return bounce(_from_python_list, pylist[1:], scmlist, cont)
def done_rest(rest):
return bounce(cont, cons(saved_first_exp, rest))
def to_python_list(scmlist):
return pogo_stick(bounce(_to_python_list, scmlist, [], lambda d:d))
def got_first(first):
nonlocal pylist
pylist.append(first)
return bounce(_to_python_list, scmlist[1], pylist, cont)
def done_rest(rest):
self.consume(tokens, TOKEN_TYPE_RPAREN)
return bounce(cont, rest)
def to_str(p):
return pogo_stick(bounce(_to_str, p, lambda d:d))
def make_quote(word):
return bounce(cont, lib_list(tsym('quote'), word))
def from_python_list(pylist):
return pogo_stick(bounce(_from_python_list, list(reversed(pylist)), NIL, lambda d:d))
