ISO/IEC INTERNATIONAL STANDARD 13211-1 First edition 1995-06-01 Information technology -- Programming languages Prolog Part 1: General core Technologies de I'information -- Langages de programmation - Prolog - Partie 1:Noyaugenéral Tso E( Reference number ISO/IEC 13211-1:1995(E) Copyright Intemational Organization for Standardization Not for Resale ISO/IEC 13211-1 : 1995(E) Contents Page Foreword vili Introduction ix Scope 1 1.1 Notes 2 Normative references 1 3 Definitions 2 Symbols and abbreviations 10 4.1 Notation 10 4.1.1 Basic mathematical types 10 4.1.2 Mathematical and set operators 10 4.1.3 Otherfunctions 10 4.2 Abstract data type: stack 11 4.3 Abstract data type: mapping 11 5 Compliance 11 5.1 Prolog processor 11 5.2 Prolog text 12 5.3 Prolog goal 12 5.4 Documentation 12 5.5 Extensions 12 5.5.1 Syntax 12 5.5.2 Predefined operators 12 5.5.3 Character-conversion mapping 12 5.5.4 Types . 12 5.5.5 Directives 13 5.5.6 Side effects 13 5.5.7 Control constructs 13 5.5.8 Flags.. 13 5.5.9 Built-in predicates 13 @ISO/IEC 1995 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopyingandmicrofilm,without permissionin writingfrom thepublisher. ISO/IEC Copyright Office·Case Postale 56·CH-1211 Geneve 20·Switzerland Printed in Switzerland Copyright Intemational Organization for Standardization from IHS Not for Resale ISO/IEC 13211-1 : 1995(E) @ ISO/IEC 1995 5.5.10 Evaluable functors . 13 5.5.11 Reserved atoms . 13 6 Syntax 13 6.1 Notation 13 6.1.1 Backus Naur Form 13 6.1.2 Abstract term syntax 14 6.2 Prolog text and data . 15 6.2.1 Prolog text 15 6.2.2 Prolog data . 15 6.3 Terms 15 6.3.1 Atomic terms 16 6.3.2 Variables 16 6.3.3 Compound terms functional notation 16 6.3.4 Compound terms -- operator notation. 17 6.3.5 Compound terms -- list notation 19 6.3.6 Compound terms - curly bracketed term 20 6.3.7 Terms - double quoted list notation 20 6.4 Tokens 20 6.4.1 Layout text. 21 6.4.2 Names 21 6.4.3 Variables 23 6.4.4 Integer numbers 23 6.4.5 Floating point numbers 23 6.4.6 Double quoted lists 24 6.4.7 Back quoted strings. 24 6.4.8 Other tokens. 24 6.5 Processor character set 24 6.5.1 Graphic characters 25 6.5.2 Alphanumeric characters 25 6.5.3 Solo characters 25 6.5.4 Layout characters 25 6.5.5 Meta characters . 26 6.6 Collating sequence 26 7 Language concepts and semantics 26 7.1 Types 27 7.1.1 Variable 27 7.1.2 Integer 27 7.1.3 Floating point 28 7.1.4 Atom. 29 7.1.5 Compound term 29 7.1.6 Related terms 29 7.2 Term order 30 7.2.1 Variable 31 7.2.2 Floating point 31 7.2.3 Integer 31 7.2.4 Atom 31 7.2.5 Compound 31 7.3 Unification 31 7.3.1 The mathematical definition 31 7.3.2 Herbrand algorithm 31 7.3.3 Subject to occurs-check (STO) and not subject to occurs- check (NSTO). 33 7.3.4 Normal unification in Prolog 33 7.4 Prolog text 33 7.4.1 Undefined features 34 ili Copyright Intermational Organization for Standardization Provided by IHS unde from IHS Not for Resale IS0/IEC 13211-1 : 1995(E) @ ISO/IEC 1995 7.4.2 Directives 34 7.4.3 Clauses 35 7.5 Database.. 36 7.5.1 Preparing a Prolog text for execution 36 7.5.2 Static and dynamic procedures . 36 7.5.3 Private and public procedures . 36 7.5.4 A logical database updale 37 7.6 Converting a term to a clause, and a clause to a term 37 7.6.1 Converting a term to the head of a clause 37 7.6.2 Converting a term to the body of a clause. . . 37 7.6.3 Converting the head of a clause to a term . 37 7.6.4 Converting the body of a clause to a term. . 38 7.7 Executing a Prolog goal 38 7.7.1 Execution. 38 7.7.2 Data types for the execution model. 38 7.7.3 Initialization 39 7.7.4 A goal succeeds 39 7.7.5 A goal fails 39 7.7.6 Re-executing a goal. 39 7.7.7 Selecting a clause for execution 40 7.7.8 Backtracking 40 7.7.9 Side effects 40 7.7.10 Executing a user-defined procedure 40 7.7.11 Executing a user-defined procedure with no more clauses 42 7.7.12 Executing a built-in pr