added explicit c cast to scalar.Cast.c_code... this should eliminate compiler warnings

theano/scalar/basic.py

@@ -219,6 +219,7 @@ class Scalar(Type):
                 + operator_eq % dict(mytype='theano_complex64')
 
     def c_code_cache_version(self):
+        #return ()
         return (3,)  #explicit T given in specialization of operator= lines.  This makes it compile with open64
         #2,
 
@@ -855,12 +856,22 @@ class Cast(UnaryScalarOp):
     def impl(self, input):
         return self.ctor(input)
     def c_code(self, node, name, (x, ), (z, ), sub):
-        return "%(z)s = %(x)s;" % locals()
+        #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)
     def grad(self, (x, ), (gz, )):
         if x.type in grad_types:
           return [cast(gz, x.type.dtype)]
         else:
           return None,
+    def c_code_cache_version(self):
+        s = super(Cast, self).c_code_cache_version()
+        if s:
+            return (2,) + s
+        else:
+            return s
 
 convert_to_int8 = Cast(int8, name='convert_to_int8')
 convert_to_int16 = Cast(int16, name='convert_to_int16')