Miscellaneous: comments, error message to point people towards using scalar

theano/tensor/basic.py

@@ -95,7 +95,11 @@ def as_tensor(x, name = None):
     try:
         return constant(x)
     except TypeError:
-        raise TypeError("Cannot convert %s to Tensor" % x, type(x))
+        try:
+            str_x = str(x)
+        except:
+            str_x = repr(x)
+        raise TypeError("Cannot convert %s to Tensor" % str_x, type(x))
 
 # this has a different name, because _as_tensor is the function which ops use
 # to upcast their arguments... this internal-use function is a good place to put debugging stuff, better than the global astensor.
@@ -506,6 +510,8 @@ class _tensor_py_operators:
     #TRANSPOSE
     T = property(lambda self: transpose(self))
 
+    shape = property(lambda self: shape(self))
+
     #SLICING
 #     def __getitem__(self, args): return Subtensor.from_idxs(self,
 #             args).outputs[0]
@@ -542,13 +548,19 @@ class _tensor_py_operators:
     
 
 class TensorResult(Result, _tensor_py_operators):
-    pass
+    """Subclass to add the tensor operators to the basic `Result` class."""
 
 class TensorConstant(Constant, _tensor_py_operators):
-    pass
+    """Subclass to add the tensor operators to the basic `Constant` class.
+    
+    To create a TensorConstant, use the `constant` function in this module.
+    """
 
 class TensorValue(Value, _tensor_py_operators):
-    pass
+    """Subclass to add the tensor operators to the basic `Value` class.
+    
+    To create a TensorValue, use the `value` function in this module.
+    """
 
 #QUESTION: why are we doing this!?
 elemwise.as_tensor = as_tensor    
@@ -1428,6 +1440,8 @@ class Join(Op):
     Of course, TensorResult instances don't have a shape, so this error can't be caught until
     runtime.  See `perform()`.
 
+    For joins involving scalar values, see @stack.
+
     .. python::
         
         x, y, z = tensor.matrix(), tensor.matrix(), tensor.matrix()
@@ -1447,6 +1461,9 @@ class Join(Op):
         as_tensor_args= [as_tensor(x) for x in tensors]
         dtypes = [x.type.dtype for x in as_tensor_args]
 
+        if not all(targs.type.ndim for targs in as_tensor_args):
+            raise TypeError('Join cannot handle arguments of dimension 0. For joining scalar values, see @stack');
+
         if not all([dtypes[0] == dt for dt in dtypes[1:]]):
             # Note that we could automatically find out the appropriate dtype
             # able to store the concatenation of all tensors, but for now we
@@ -1468,7 +1485,10 @@ class Join(Op):
                 raise ValueError('Dimensions other than the given axis must'
                     ' match', tensors)
             bcastable[:] = as_tensor_args[0].type.broadcastable
-            bcastable[axis] = False
+            try:
+                bcastable[axis] = False
+            except IndexError, e:
+                raise ValueError('Join argument "axis" is out of range (given input dimensions)')
 
         inputs = [as_tensor(axis)] + as_tensor_args
         if inputs[0].type not in int_types: