[ADD] composition function utility

bzr revid: xmo@openerp.com-20130925145205-vumu9cgr5kob0900

openerp/tests/__init__.py

@@ -22,6 +22,7 @@ import test_translate
 import test_uninstall
 import test_view_validation
 import test_qweb
+import test_func
 # This need a change in `oe run-tests` to only run fast_suite + checks by default.
 # import test_xmlrpc
 
@@ -43,6 +44,7 @@ checks = [
     test_osv,
     test_translate,
     test_qweb,
+    test_func,
 ]
  
 # vim:expandtab:smartindent:tabstop=4:softtabstop=4:shiftwidth=4:

openerp/tests/test_func.py

@@ -0,0 +1,22 @@
+# -*- coding: utf-8 -*-
+import functools
+import unittest2
+
+from ..tools.func import compose
+
+class TestCompose(unittest2.TestCase):
+    def test_basic(self):
+        str_add = compose(str, lambda a, b: a + b)
+        self.assertEqual(
+            str_add(1, 2),
+            "3")
+
+    def test_decorator(self):
+        """ ensure compose() can be partially applied as a decorator
+        """
+        @functools.partial(compose, unicode)
+        def mul(a, b):
+            return a * b
+
+        self.assertEqual(mul(5, 42), u"210")
+

openerp/tools/func.py

@@ -57,4 +57,19 @@ def frame_codeinfo(fframe, back=0):
     except Exception:
         return "<unknown>", ''
 
+def compose(a, b):
+    """ Composes the callables ``a`` and ``b``. ``compose(a, b)(*args)`` is
+    equivalent to ``a(b(*args))``.
+
+    Can be used as a decorator by partially applying ``a``::
+
+         @partial(compose, a)
+         def b():
+            ...
+    """
+    @wraps(b)
+    def wrapper(*args, **kwargs):
+        return a(b(*args, **kwargs))
+    return wrapper
+
 # vim:expandtab:smartindent:tabstop=4:softtabstop=4:shiftwidth=4: