Language Reference/Clauses - Revision history

Thomas Linder Puls: consistenty

2012-10-26T08:47:27Z

consistenty

← Older revision		Revision as of 10:47, 26 October 2012
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	{{languageReferenceNavbar\|Clauses}}		{{languageReferenceNavbar\|Clauses}}

	=== Clauses ~~Section~~ ===		=== Clauses Sections ===

	A <vp>clauses</vp> section consists of a set of clauses. The <vp>clauses</vp> section contains implementations of predicates or initial values of facts.		A <vp>clauses</vp> section consists of a set of clauses. The <vp>clauses</vp> section contains implementations of predicates or initial values of facts.

Thomas Linder Puls: /* Goal Section */ procedure goal

2012-10-24T13:14:28Z

Goal Section: procedure goal

← Older revision		Revision as of 15:14, 24 October 2012
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	The <vp>goal</vp> section consists of a clause body. The <vp>goal</vp> section defines its own scope, therefore all invocations should contain class qualifications.		The <vp>goal</vp> section consists of a clause body. The <vp>goal</vp> section defines its own scope, therefore all invocations should contain class qualifications.

	~~Normally, the~~ goal must have <vp>procedure</vp> mode.		The goal must have <vp>procedure</vp> mode.

Thomas Linder Puls: Guards ref

2010-03-15T13:58:57Z

Guards ref

← Older revision		Revision as of 15:58, 15 March 2010
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	<vipbnf><ClauseBody> :		<vipbnf><ClauseBody> :
	:- <Term></vipbnf>		:- <Term></vipbnf>

			See also {{lang2\|Monitors\|Guards\|Guards}} in {{lang\|Monitors\|Monitors}}.

	=== Goal Section ===		=== Goal Section ===

Thomas Linder Puls: Guards ref

2010-03-15T13:47:52Z

Guards ref

← Older revision		Revision as of 15:47, 15 March 2010
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	<vipbnf><ClausesSection> :		<vipbnf><ClausesSection> :
	clauses <Clause>-dot-term-list-opt</vipbnf>		clauses <Clause>-dot-term-list-opt</vipbnf>

			See also {{lang2\|Monitors\|Guards\|Guards}} in {{lang\|Monitors\|Monitors}}.

	=== Clauses ===		=== Clauses ===

Thomas Linder Puls: header levels

2008-10-14T22:12:02Z

header levels

← Older revision		Revision as of 00:12, 15 October 2008
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	{{languageReferenceNavbar\|Clauses}}		{{languageReferenceNavbar\|Clauses}}

	== Clauses Section ==		=== Clauses Section ===

	A <vp>clauses</vp> section consists of a set of clauses. The <vp>clauses</vp> section contains implementations of predicates or initial values of facts.		A <vp>clauses</vp> section consists of a set of clauses. The <vp>clauses</vp> section contains implementations of predicates or initial values of facts.
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	clauses <Clause>-dot-term-list-opt</vipbnf>		clauses <Clause>-dot-term-list-opt</vipbnf>

	== Clauses ==		=== Clauses ===

	Clauses are used to define predicates. A single predicate is defined by a set of clauses. Each clause is executed in turn until one of them '''''succeeds''''', or there is no more clauses left to execute. If no clause succeeds the predicate '''''fails'''''.		Clauses are used to define predicates. A single predicate is defined by a set of clauses. Each clause is executed in turn until one of them '''''succeeds''''', or there is no more clauses left to execute. If no clause succeeds the predicate '''''fails'''''.
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	:- <Term></vipbnf>		:- <Term></vipbnf>

	== Goal Section ==		=== Goal Section ===

	The <vp>goal</vp> section is the entry to a program. When the program starts it executes the <vp>goal</vp>, when the <vp>goal</vp> is executed, the program exits.		The <vp>goal</vp> section is the entry to a program. When the program starts it executes the <vp>goal</vp>, when the <vp>goal</vp> is executed, the program exits.

Thomas Linder Puls: 1 revision(s)

2008-09-15T14:22:11Z

1 revision(s)

← Older revision	Revision as of 16:22, 15 September 2008
(No difference)

Thomas Linder Puls: /* Clauses */

2008-09-15T13:22:17Z

Clauses

New page

{{languageReferenceNavbar|Clauses}}

== Clauses Section ==

A <vp>clauses</vp> section consists of a set of clauses. The <vp>clauses</vp> section contains implementations of predicates or initial values of facts.

A single clause section can have clauses for several predicates and facts. On the other hand, all clauses for one predicate/fact (the same name and arity) must be grouped together in one clauses section and without intervening clauses of other predicates/facts.

<vipbnf><ClausesSection> :
clauses <Clause>-dot-term-list-opt</vipbnf>

== Clauses ==

Clauses are used to define predicates. A single predicate is defined by a set of clauses. Each clause is executed in turn until one of them '''''succeeds''''', or there is no more clauses left to execute. If no clause succeeds the predicate '''''fails'''''.

If a clause '''''succeeds''''' and there are more relevant clauses in a predicate left, the program control can later '''''backtrack''''' to the clauses of this predicate to search for other solutions.

Thus, a predicate can '''fail''', '''''succeed''''', and even '''''succeed''''' multiple times.

Each clause has a head and optionally a body.

When a predicate is called the clauses are tried in turn (from top to bottom). For each clause the head is unified with the arguments from the call. If this unification succeeds then the body of the clause (if such one exist) is executed. The clause '''''succeeds''''' if the match of the head '''''succeeds''''' and the body '''''succeeds'''''. Otherwise it '''''fails'''''.

A clause consists of a head and an optional body.

<vipbnf><Clause> :
<ClauseHead> <ReturnValue>-opt <ClauseBody>-opt .</vipbnf>

<vipbnf><ClauseHead> :
<LowercaseIdentifier> ( <Term>-comma-sep-list-opt )</vipbnf>

<vipbnf><ReturnValue> :
= <Term></vipbnf>

<vipbnf><ClauseBody> :
:- <Term></vipbnf>

== Goal Section ==

The <vp>goal</vp> section is the entry to a program. When the program starts it executes the <vp>goal</vp>, when the <vp>goal</vp> is executed, the program exits.

<vipbnf><GoalSection> :
goal <Term>.</vipbnf>

The <vp>goal</vp> section consists of a clause body. The <vp>goal</vp> section defines its own scope, therefore all invocations should contain class qualifications.

Normally, the goal must have <vp>procedure</vp> mode.