Boolean-valued loops

A new control structure construct, the while-until, is introduced as a syntactic combination of the while statement and the repeat-until statement. Examples show that the use of the while-until can lead to structured programs that are conceptually more manageable than those attainable without it. The while-until statement is then extended to a value-returning expression which is shown to be more powerful than the classical looping structures. It is shown to be equivalent in power to those structures with exit when a value-returning if-then-else is allowed. As a consequence, there are flowcharts whose implementations require control structures stronger than the while-until. Implementation details are discussed and Hoare-like axioms are presented. A closing discussion on oesthetics discourages some natural generalizations, but it concludes that the basic while-until is convenient for all parties on a programming team: coder, reader, compiler, and validator.