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# Licensed to the Apache Software Foundation (ASF) under one
# or more contributor license agreements. See the NOTICE file
# distributed with this work for additional information
# regarding copyright ownership. The ASF licenses this file
# to you under the Apache License, Version 2.0 (the
# "License"); you may not use this file except in compliance
# with the License. You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing,
# software distributed under the License is distributed on an
# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
# KIND, either express or implied. See the License for the
# specific language governing permissions and limitations
# under the License.
# Simple utility functions
from sys import maxint
# Scheme-like lists
def cons(a, b):
return (a,) + b
def car(l):
return l[0]
def first(l):
return car(l)
def cdr(l):
return l[1:]
def rest(l):
return cdr(l)
def cadr(l):
return car(cdr(l))
def cddr(l):
return cdr(cdr(l))
def caddr(l):
return car(cddr(l))
def cdddr(l):
return cdr(cdr(cdr(l)))
def cadddr(l):
return car(cdddr(l))
def append(a, b):
return a + b
def reverse(l):
r = list(l)
r.reverse()
return tuple(r)
def isNil(l):
if isinstance(l, streampair):
return l.isNil()
return l == ()
def isSymbol(v):
return isinstance(v, basestring) and v[0:1] == "'"
def isString(v):
return isinstance(v, basestring) and v[0:1] != "'"
def isList(v):
if getattr(v, '__iter__', False) == False:
return False
if isinstance(v, basestring) or isinstance(v, dict):
return False
return True
def isTaggedList(v, t):
return isList(v) and not isNil(v) and car(v) == t
# Scheme-like streams
class streampair(object):
def __init__(self, car, cdr):
self.car = car
self.cdr = cdr
def __repr__(self):
return repr(self[0:len(self)])
def isNil(self):
return self.cdr == ()
def __len__(self):
if self.cdr == ():
return 0
return 1 + len(self.cdr())
def __getitem__(self, i):
if i == 0:
return self.car
return self.cdr()[i - 1]
def __getslice__(self, i, j):
if isNil(self):
return ()
if i > 0:
if j == maxint:
return self.cdr()[i - 1: j]
return self.cdr()[i - 1: j - 1]
if j == maxint:
return self
if j == 0:
return (self.car,)
return (self.car,) + self.cdr()[: j - 1]
def __eq__(self, other):
sl = len(self)
ol = len(other)
if sl != ol:
return False
return self[0: sl] == other[0: ol]
def __ne__(self, other):
return not self.__eq__(other)
def cons_stream(car, cdr):
return streampair(car, cdr)
# Scheme-like associations
def assoc(k, l):
if l == ():
return None
if k == car(car(l)):
return car(l)
return assoc(k, cdr(l))
# Currying / partial function application
def curry(f, *args):
return lambda *a: f(*(args + a))
# Convert a path represented as a list of values to a string
def path(p):
if isNil(p):
return ""
return "/" + car(p) + path(cdr(p))
# Split a path into a list of segments
def tokens(path):
return tuple(filter(lambda s: len(s) != 0, path.split("/")))
# Return true if s1 contains s2
def contains(s1, s2):
return s1.find(s2) != -1
# Write a list of strings to a stream
def writeStrings(l, os):
if l == ():
return os
os.write(car(l))
return writeStrings(cdr(l), os)
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