  We discuss the possibility of constructing a function that validates the
definition or not definition of the partial recursive functions of one
variable. This is a topic in computability theory, which was first approached
by Alan M. Turing in 1936 in his foundational work "On Computable Numbers".
Here we face it using the Model of computability of the recursive functions
instead of the Turing's machines, but the results are transferable from one to
another paradigm with ease. Recursive functions that are not defined at a given
point, correspond to the Turing machines that "do not end" for a given input.
What we propose Is a slight slip from the orthodox point of view: the issue of
the self-reference and of the self-validation is not an impediment in
imperative languages.
