Transformat ions that Preserve

A b s t r a c t . We consider transformations (performed by general recursive operators) mapping recursive functions into recursive functions. These transformations can be considered as mapping sets of recursive functions into sets of recursive functions. A transformation is said to be preserving the identification type I, if the transformation always maps/-identifiable sets into/-identifiable sets. There are transformations preserving FIN but not EX, and there axe transformations preserving EX but not FIN. However, transformations preserving EXi always preserve EXj for j < i.