Thomas N. Hibbard

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This paper introduces an abstract entity, the binary search tree, and exhibits some of its properties. The properties exhibited are relevant to processes occurring in stored program computers-in particular, to search processes. The discussion of this relevance is deferred until Section 2. Section 1 constitutes the body of the paper. Section 1.1 consists of(More)
techniques previously published. The additional space required is one word per record. Therefore, given a memory area of size A and a record of size S, then the number of records (N) tha t can be sequenced in memory using the Replacement-Selection technique is A/(S+i) , as compared to A/S for other techniques. If the additional memory is not available, then(More)
In this paper is considered the problem, first introduced in [1], of determining the state of a sequential machine. I t is assumed that information about the state of a machine can be obtained only by applying an input and observing the machine's response (output) . The application of an input generally causes a machine to change state; this terminal state(More)
A phrase structure grammar is called <italic>context-limited</italic> if there exists a partial ordering on its alphabet such that any letter on the left of any production is less than some letter on the right of the same production. It is proved that context-limited grammars are equivalent to context-free grammars, the equivalence including ambiguity. The(More)
Call a (context-free) language unambiguous if it is not inherently ambiguous. In the absence of evidence to the contrary, the suspicion has arisen that the unambiguous languages might be precisely those languages with context-free complements. The two theorems presented in this paper lay the suspicion to rest by providing (1) an inherently ambiguous(More)
A preliminary example of program development demonstrates that the control-independent implementation of data types can lead to very inefficient code. The concept of a data space, which emphasizes the interaction between data and control structures, is introduced as a formal model of virtual machines. The model consists of three components: a state space X,(More)