Add simple implementation of Scheme-like lazy streams.

git-svn-id: http://svn.us.apache.org/repos/asf/tuscany@943806 13f79535-47bb-0310-9956-ffa450edef68

3 files changed, 114 insertions, 1 deletions

diff --git a/sca-cpp/trunk/modules/wsgi/stream-test.py b/sca-cpp/trunk/modules/wsgi/stream-test.py
new file mode 100755
index 0000000000..2cff038f1e
--- /dev/null
+++ b/sca-cpp/trunk/modules/wsgi/stream-test.py
@@ -0,0 +1,47 @@
+#!/usr/bin/python
+#  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.
+
+# Test stream functions
+
+import unittest
+from util import *
+
+def testStream():
+
+    s = cons_stream(0, lambda: cons_stream(1, lambda: cons(2, ())))
+    assert len(s) == 3
+    assert car(s) == 0
+    assert cadr(s) == 1
+    assert len(cdr(s)) == 2
+    assert s[0] == 0
+    assert s[1] == 1
+    assert s[2] == 2
+    assert s[:1] == (0, 1)
+    assert s[:5] == (0, 1, 2)
+    assert s[2:5] == (2,)
+    assert s[4:5] == ()
+    assert s[0:] == (0, 1, 2)
+    assert (0, 1, 2) == s[0:]
+
+    return True
+
+if __name__ == "__main__":
+    print "Testing..."
+    testStream()
+    print "OK"
+
diff --git a/sca-cpp/trunk/modules/wsgi/util-test b/sca-cpp/trunk/modules/wsgi/util-test
index a1c54e80f1..cb4e2f6c8a 100755
--- a/sca-cpp/trunk/modules/wsgi/util-test
+++ b/sca-cpp/trunk/modules/wsgi/util-test
@@ -21,9 +21,13 @@
 here=`readlink -f $0`; here=`dirname $here`
 python_prefix=`cat $here/../python/python.prefix`
 
-$python_prefix/bin/python xml-test.py
+$python_prefix/bin/python stream-test.py
 rc=$?
 if [ "$rc" = "0" ]; then
+    $python_prefix/bin/python xml-test.py
+    rc=$?
+fi
+if [ "$rc" = "0" ]; then
     $python_prefix/bin/python atom-test.py
     rc=$?
 fi
diff --git a/sca-cpp/trunk/modules/wsgi/util.py b/sca-cpp/trunk/modules/wsgi/util.py
index d945c7bdef..560101e32d 100644
--- a/sca-cpp/trunk/modules/wsgi/util.py
+++ b/sca-cpp/trunk/modules/wsgi/util.py
@@ -16,6 +16,7 @@
 #  under the License.
 
 # Simple utility functions
+from sys import maxint
 
 # Scheme-like lists
 def cons(a, b):
@@ -23,10 +24,16 @@ def cons(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))
 
@@ -36,12 +43,17 @@ def cddr(l):
 def caddr(l):
     return car(cddr(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):
@@ -57,6 +69,56 @@ def isList(v):
 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 == ():