From the implementation point of view, such a rule is also important to improve the evaluation of function calls in a number of different ways: efficiency, speed, termination behavior, etc. In programming languages design, a clear rule to select the arguments of functions that are evaluated in function calls is essential to understand the program behavior. Unlike von Neumann languages, these systems have semantics loosely coupled to states-only one state transition occurs per major computation.

General theorems of the algebra give the detailed behavior and termination conditions for large classes of programs.Ī new class of computing systems uses the functional programming style both in its programming language and in its state transition rules.

Combining forms are chosen not only for their programming power but also for the power of their associated algebraic laws. These transformations are given by algebraic laws and are carried out in the same language in which programs are written. This algebra can be used to transform programs and to solve equations whose “unknowns” are programs in much the same way one transforms equations in high school algebra. Combining forms can use high level programs to build still higher level ones in a style not possible in conventional languages.Īssociated with the functional style of programming is an algebra of programs whose variables range over programs and whose operations are combining forms. Functional programs deal with structured data, are often nonrepetitive and nonrecursive, are hierarchically constructed, do not name their arguments, and do not require the complex machinery of procedure declarations to become generally applicable. Inherent defects at the most basic level cause them to be both fat and weak: their primitive word-at-a-time style of programming inherited from their common ancestor-the von Neumann computer, their close coupling of semantics to state transitions, their division of programming into a world of expressions and a world of statements, their inability to effectively use powerful combining forms for building new programs from existing ones, and their lack of useful mathematical properties for reasoning about programs.Īn alternative functional style of programming is founded on the use of combining forms for creating programs. Conventional programming languages are growing ever more enormous, but not stronger.

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