YAP Core Built-ins

Detailed Description

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

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

Modules
	Predicates on Atoms and Strings
	The following predicates are used to manipulate atoms, strings, lists of codes and lists of chars.
	The Blackboard
	YAP implements a blackboard in the style of the SICStus Prolog blackboard.
	Copying Terms
	Internal Data Base
	Some programs need global information for, e.g.
	Supporting features of the Prolog language.
	Prolog includes a number of features that allow program and predicate manipulation.
	Arithmetic in YAP
	Prolog Flags
	Input/Output Predicates
	⁸
	Control Predicates
	Dialects
	Error generating type-checking
	This code is based oon the SWI predicates to simplify error generation and checking.
	Grammar Rules
	Grammar rules in Prolog are both a convenient way to express definite clause grammars and an extension of the well known context-free grammars.
	list predicates in a module
	Operators
	Collecting Solutions to a Goal
	When there are several solutions to a goal, if the user wants to collect all the solutions he may be led to use the data base, because backtracking will forget previous solutions.
	System Status
	Term Manipulation
	Top-Level and Boot Predicates