fixed hack in Cast c code in scalar basic

theano/scalar/basic.py

@@ -880,11 +880,7 @@ class Cast(UnaryScalarOp):
     def impl(self, input):
         return self.ctor(input)
     def c_code(self, node, name, (x, ), (z, ), sub):
-        #HACK: we assume that x has the form 'VARNAME_i', 
-        #      and we need the varname to get the dtype.
-        assert (len(x) > 2) and (x[-2:] == '_i')
-        varname = x[:-2]
-        return "%s = (dtype_%s)%s;" % (z, varname, x)
+        return "%s = (%s)%s;" % (z, node.outputs[0].type.dtype_specs()[1], x)
     def grad(self, (x, ), (gz, )):
         if x.type in grad_types:
           return [cast(gz, x.type.dtype)]
@@ -893,7 +889,7 @@ class Cast(UnaryScalarOp):
     def c_code_cache_version(self):
         s = super(Cast, self).c_code_cache_version()
         if s:
-            return (2,) + s
+            return (3,) + s
         else:
             return s