yap-6.3/docs/md/core.md

@defgroup builtins Core Built-ins

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This chapter describes the core built-in predicates that control the execution of Prolog programs, provide fundamental functionality such as termm manipulation or arithmetic, and support interaction with external resources.

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Many of the predicates described here have been standardised by the International Standard Organization. The corresponding standartised subset of Prolog also known as ISO-Prolog.

In the description of the arguments of predicates the following notation will be used:

• a preceding plus sign will denote an argument as an "input argument" - the argument is read, not written, and it cannot be a free variable at the time of the call;

• a preceding minus sign will denote an "output argument";

• an argument with no preceding symbol can be used in both ways.

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