Method for selective back-tracking in a hierarchical system containing a flag which indicates the validity of a choice-point

摘要

A method of back-tracking in a computer processing operation in which the programmer can be provided with a number of different types of the back-track controlling, from which a suitable one can freely be selected in accordance with the need of the programmer. In this method, a flag is provided in each choice point, for indicating a type of back- track controlling, and a stack which contains an address of a choice point specified as a present choice point by a present choice point register and an address of a preceding choice point which is immediately preceding the present choice point is utilized in changing indication of the flag.