One of the difficulties in using nondeterministic algorithms for the solution of combinatorial problems is that most programming languages do not include features capable of easily repre-senting backtracking processes. This paper describes a procedure mechanism that uses co-routines as a means for the description and realization of nondeterministic algorithms. A solution to the eight queens problem is given to illustrate the application of the procedure mechanism to backtracking problems. I.

This paper describes CBack, a simple, but general tool for backtrack programming in the programming language C. The use of the tool is illustrated through examples of a tutorial nature. In addition to the usual depth-first search strategy, CBack provides for the more general heuristic best-first search strategy. The implementation of CBack is described in detail. The source code, shown in its full length, is entirely written in ANSI C and highly portable across diverse computer architectures and C compilers

Abstract-Programming languages which use dynamic identification for free variables (i.e., non-local referencest are generally implemented with a deep or shallow binding variable access strategy. In this paper, variable access through the binding environment is assumed to be desir-able. Given this assumption, it is demonstrated that the act of assigning values to variables may yield unexpected results for some of the binding strategies when functional arguments and results are used. A number of variations of deep and shallow binding strategies are examined along with the modifications necessary to implement the assignment operation in the expected manner Deep binding Shallow binding Dynamic binding Access environments Functional argu-ments Binding environments Activation environments

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