add stream

Author: czheo

README.md

@@ -184,4 +184,19 @@ def push(lst, x):
 # returns [1,2,3]
 ```
 
+### stream
+
+``` python
+from syntax_sugar import stream, take
+
+list(stream() << [1,2,3] << range(5))
+# [1,2,3,0,1,2,3,4]
+# stream will connect all sequences together
+
+list((stream() << [1, 1] << (lambda x, y: x + y)) /take/ 10)
+# [1, 1, 2, 3, 5, 8, 13, 21, 34, 55]
+# This is the first 10 items of an infinite fibonacci stream
+# If a function is met, it will infinitely take the last N previous items to generate the next item.
+```
+
 More receipes: https://github.com/czheo/syntax_sugar_python/tree/master/recipes

syntax_sugar/__init__.py

@@ -2,3 +2,4 @@
 from .composable import *
 from .pipe import *
 from .infix import *
+from .stream import *

syntax_sugar/composable.py

@@ -8,11 +8,11 @@
 ]
 
 class composable(partial):
-    def __mul__(self, func):
-        return lambda *args, **kwargs: self(func(*args, **kwargs))
+    def __mul__(self, rhs):
+        return lambda *args, **kwargs: self(rhs(*args, **kwargs))
 
-    def __rmul__(self, func):
-        return lambda *args, **kwargs: func(self(*args, **kwargs))
+    def __rmul__(self, lhs):
+        return lambda *args, **kwargs: lhs(self(*args, **kwargs))
 
 def compose(*args):
     return reduce(lambda acc, fn:

syntax_sugar/stream.py

@@ -0,0 +1,50 @@
+from itertools import chain
+from inspect import getfullargspec
+
+__all__ = [
+    'stream',
+]
+
+class StreamIter:
+    def __init__(self, fn, data):
+        self.fn = fn
+        self.fn_argc = len(getfullargspec(fn).args)
+        self.data = data
+        self.prev = []
+
+    def __iter__(self):
+        return self
+
+    def __next__(self):
+        try:
+            ret = next(self.data)
+            self.prev.append(ret)
+            while len(self.prev) > self.fn_argc:
+                self.prev.pop(0)
+            return ret
+        except StopIteration:
+            ret = self.fn(*self.prev)
+            self.prev.append(ret)
+            while len(self.prev) > self.fn_argc:
+                self.prev.pop(0)
+            return ret
+
+class stream:
+    def __init__(self, data = None):
+        if data is None:
+            self.data = iter([])
+        else:
+            self.data = iter(data)
+
+    def __iter__(self):
+        return self
+
+    def __next__(self):
+        return next(self.data)
+    
+    def __lshift__(self, rhs):
+        if hasattr(rhs, '__iter__'):
+            self.data = chain(self.data, rhs)
+        elif hasattr(rhs, '__call__'):
+            self.data = StreamIter(rhs, self.data)
+        return self

tests/test_stream.py

@@ -0,0 +1,10 @@
+from syntax_sugar import *
+
+def test_stream_collection():
+    assert list(stream() << [1,2,3] << [4,5,6]) == list([1,2,3,4,5,6])
+    assert list(stream() << [1,2,3] << range(4,7)) == list([1,2,3,4,5,6])
+
+def test_stream_function():
+    assert list((stream() << [1,2,3] << (lambda x: x+1)) /take/ 5) == list([1,2,3,4,5])
+    assert list((stream() << [1,2,3] << (lambda x: x+1)) /drop/ 3 /take/ 5) == list([4,5,6,7,8])
+    assert list((stream() << range(1,10) << (lambda x: x+1)) /drop/ 3 /take/ 5) == list([4,5,6,7,8])