W. W. Peterson, T. Kasami, and N. Tokura, On the capabilities of while, repeat, and exit statements, Communications of the ACM, 16 (1973), pp. 503--512.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....normal form if it is a finite tree like schema whose branches may only bend back to ancestor nodes. The literature on looping constructs in programming languages is replete with results on operations with single entry points and multiple exits. Here we limit ourselves to mentioning the references [9, 10, 22]. In particular, Peterson et al. defined in [22] a well formed program to be one in which all control structures have a single entry point, and showed that such a program need only use IF THEN, DO FOREVER, and multi level loop EXIT statements as control structures. Since the addition of ....

....may only bend back to ancestor nodes. The literature on looping constructs in programming languages is replete with results on operations with single entry points and multiple exits. Here we limit ourselves to mentioning the references [9, 10, 22] In particular, Peterson et al. defined in [22] a well formed program to be one in which all control structures have a single entry point, and showed that such a program need only use IF THEN, DO FOREVER, and multi level loop EXIT statements as control structures. Since the addition of multi exit iteration to a process algebra like BPA ....

W. W. Peterson, T. Kasami, and N. Tokura, On the capabilities of while, repeat, and exit statements, Communications of the ACM, 16 (1973), pp. 503--512.

....At the same time, it became apparent that not all uses of GOTO were harmful. For example, using a GOTO to perform a multi level exit from nested WHILE DO loops was much clearer than the GOTO less alternative; it was generally GOTOs into control structures, not out of them, that were harmful. In [PKT73], Peterson et al. defined a well4 formed program to be one in which all control structures have a single entry point, and showed that such a program need only use IF THEN, DO FOREVER, and multi level loop EXIT statements as control structures. The single entry property of well formed programs ....

W. W. Peterson, T. Kasami, and N. Tokura. On the capabilities of while, repeat, and exit statements. Communications of the ACM, 16(8):503--512, 1973.

....to set, test, and reset the flags. In both these cases, additional complexity is introduced into the program; this complexity is largely a consequence of the simple control structures in the programming language and not the implementation of a particular algorithm. Peterson, Kasami and Tokura [PKT73] demonstrated that some copying of code and all of the flag variables required by the Bohm and Jacopini transformation can be eliminated by using a new control structure. This control structure involves an EXIT statement and requires that some of the loops in the program be labelled. The EXIT ....

W. W. Peterson, T. Kasami, and N. Tokura. On the Capabilities of While, Repeat, and Exit Statements. Communications of the ACM, 16(8):503--512, August 1973.

....set, test, and reset the switches. In both these cases additional complexity is introduced into the program; this complexity being largely a consequence of the simple control structures in the programming language. SIGPLAN Notices, vol. 20, no. 11, November 1985, pp. 14 22 It has been shown by [PKT73] that the switches required by the Bohm and Jacopini transformation can be avoided by using a new control structure. This control structure involves a LEAVE statement and requires that some of the loops in the program be labelled. The LEAVE statement exits all containing control structures until ....

W. W. Peterson, T. Kasami, and N. Tokura. On the Capabilities of While, Repeat, and Exit Statements. Communications of the ACM, 16(8):503--512, August 1973.

....The second stage entails presenting some basic operations which allow the programmer to decide how far he wants to unfold a nested structure. Such subjective unfolding is quite useful and may even be necessary, especially for software enhancement. The method employs a process called node splitting [17]. Node splitting consists of copying and inserting single sequential blocks. There is no change of predicates and no addition of boolean variables. The continuity of the method preserves the context of the original program blocks. This process both decreases unnecessery complexity, and improves ....

....According to [2] such a structure is considered harmful. Transformation of Flow Graphs and Source Code Our main concerns in flow graph transformation are control flow graphs with underlying source code. The atomic operation which we apply on the flow graph in our apporach is node splitting [17]. In [5] we developed a mathematical model for node splitting using the cartesian product and supersets. The fundamental restriction of program transformation is the functional equivalence, which has to be preserved. Applied to the node splitting operations , the following constraint preserves the ....

W. W. Peterson, T. Kasami, and N. Tokura. On the capabilities of while, repeat, and exit statements. Communications of the ACM, 16(8):503--512, April 1973. 8 Figures

....the same time, it became apparent that not all uses of GOTO were harmful. For example, using a GOTO to perform an exit from a WHILEDO loop was often much clearer than the GOTO less alternative: it was generally GOTOs into control structures, not out of them, that were harmful. Peterson et al. PKT73] defined a wellformed program to be one in which all control structures have a single entry point; thus, being well formed is equivalent to being tree structured. They showed that such a program need only use IF THEN, DO FOREVER, and multi level loop EXIT statements as control structures. cortl ....

W. W. Peterson, T. Kasami, and N. Tokura. On the capabilities of while, repeat, and exit statements. Communications of the ACM, 16(8):503--512, 1973.

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