Add proper conversion to bool.

Author: abergeron

pygpu/gpuarray.pyx

@@ -1657,6 +1657,16 @@ cdef class GpuArray:
         """
         return pygpu_as_ndarray(self)
 
+    def __bool__(self):
+        if self.ga.nd == 0:
+            return True
+        if self.ga.nd == 1:
+            if self.ga.dimensions[0] == 0:
+                return False
+            if self.ga.dimensions[0] == 1:
+                return bool(numpy.asarray(self))
+        raise ValueError('The truth value of a multi-element array is ambiguous')
+
     def _empty_like_me(self, dtype=None, order='C'):
         """
         _empty_like_me(dtype=None, order='C')