Some more documentation

theano/scalar/basic.py

@@ -791,7 +791,12 @@ tanh = Tanh(upgrade_to_float, name = 'tanh')
 
 
 class Composite(ScalarOp):
-
+    """
+    Composite is an Op that takes a graph of scalar operations and
+    produces c code for the whole graph. Its biggest use would be to
+    implement the loop fusion optimizer (which I have yet to do
+    someday...)
+    """
     def __init__(self, inputs, outputs):
         env = Env(*gof.graph.clone(inputs, outputs))
         gof.MergeOptimizer().optimize(env)

theano/scalar/tests/test_basic.py

+"""
+These routines are not well-tested. They are also old.
+OB says that it is not important to test them well because Scalar Ops
+are rarely used by themselves, instead they are the basis for Tensor Ops
+(which should be checked thoroughly). Moreover, Scalar will be changed
+to use numpy's scalar routines.
+If you do want to rewrite these tests, bear in mind:
+  * You don't need to use Composite.
+  * Env and DualLinker are old, use compile.function instead.
+"""
 
 import unittest