Aleph, a language encouraging program hierarchy
Robert Bosch, Dick Grune, Lambert Meertens · Centrum Wiskunde & Informatica (CWI), the national research institute for mathematics and computer science in the Netherlands · 1973
An ALEPH program consists of a set of gramm~like definitio::i.s of input, actions to be performed and output, properly interrelated.The syntactic and semantic simplicity of Al.Elli has three important consequences: aspects of the dynamic behavior of the program cari be derived statically, substantial optimization can be achieved thro~gh simple algorithms, and portability is high.The aspects of the dynamic behavior include a check on the use of uninitialized variables and a consistency check on useI'--declared dynamic properties of rules.The optimizability of ALEIB programs allows the programmer to formulate algorithms wlth all the elegance inherent in a top-do;;rn :formulation and nevertheless obtain good.machine code. 1 .Introduction.ALEPH is a high-level programming language designed to induce the user to write his programs in a well-structured way.The language is suitable for any problem that suggests top-down analysis (parsers, search algorithms, co.:nbinatorial problems, artificial intelligence problems etc.).An ALEPH program is a top-down description of what is to be done: complex actions are defined in terms of (us,J.ally)less complex ones, which in turn are defined in terms of still simpler ones, and so on, until a level is reached at which further deco.:nposition is undesirable.An ALEP-.d program consists of a set of such definitions, in a notation not