Language Reference/Attributes - Revision history

Thomas Linder Puls: link

2025-08-19T15:08:25Z

link

← Older revision		Revision as of 17:08, 19 August 2025
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	The <vp>constant</vp> attribute is used to declare fact variables that cannot be changed once they have been initialized.		The <vp>constant</vp> attribute is used to declare fact variables that cannot be changed once they have been initialized.

	See {{lang2\|Facts\|Constant fact ~~variables~~\|Constant fact ~~variables~~}}.		See {{lang2\|Facts\|Constant fact variable\|Constant fact variable}}.

	==== compiletimeSetting ====		==== compiletimeSetting ====

Thomas Linder Puls: All programPoint info moved here

2024-01-04T12:14:29Z

All programPoint info moved here

← Older revision		Revision as of 14:14, 4 January 2024
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	==== programPoint ====		==== programPoint ====

	~~Used for a~~ predicate or constructor declaration to indicate that it ~~recieves~~ an extra input argument which describes the place in a program (program point) where this predicate was called. This additional argument has programPoint type which is declared in the PFC core class like:		<vp>programPoint</vp>'s are used by the exception mechanism to indicate where exceptions are raised and continued, but the usage is not limited to that purpose.

			The <vp>programPoint</vp> attribute is used predicate or constructor declaration to indicate that it receives an extra input argument which describes the place in a program (program point) where this predicate was called. This additional argument has <vp>programPoint</vp> type which is declared in the PFC core class like:

	<vip>domains		<vip>domains
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	</vip>		</vip>

	The ~~clause name of such predicate or constructor should have suffix "_explicit". Valid for~~ a predicate ~~or constructor~~ declaration.		The <vp>programPoint</vp> attribute can be added to a predicate declaration like this:

			<vip>predicates
			raiseAnException : (integer X) erroneous [programPoint].</vip>

			Adding this attribute actually means that two predicates are declared, the one you have mentioned and an another one with name <vp>raiseAnException_explicit</vp> which in addition to the arguments of <vp>raiseAnException</vp> takes a <vp>programPoint</vp> as first argument:

	~~{{Example\|~~
	<vip>predicates		<vip>predicates
	~~pred~~ : (~~string String~~) [programPoint].		raiseAnException : (integer X) erroneous.
	clauses
	~~pred_explicit~~(~~ProgramPoint, String~~) :-		predicates
	...		raiseAnException_explicit : (programPoint ProgramPoint, integer X) erroneous.</vip>

			When you call <vp>raiseAnException</vp> the compiler will create a program point and call <vp>raiseAnException_explicit</vp> instead.

			{{example\|
			<vip>clauses
			test() :-
			raiseAnException(17).</vip>
			will actually correspond to:
			<vip>clauses
			test() :-
			raiseAnException_explicit(programPoint(...), 17).
	</vip>		</vip>
	}}		where the program point corresponds to the point where <vp>raiseAnException</vp> is called in the <vp>test</vp> predicate.}}

			If you have a programPoint you can directly call the explicit predicate with it.

			{{example\|
			<vip>clauses
			raiseAnExceptio17_explicit(ProgramPoint) :-
			raiseAnException_explicit(ProgramPoint, 17).
			</vip>

			Typically, as in this example, explicit predicates will call other explicit predicates with the programPoint they receive in order to use an "original" call point in a nested explicit predicate.}}

			Such code is treated in the usual way. I.e. when calling <vp>raiseAnException</vp> or <vp>raiseAnException_explicit</vp> will in both cases result in calling <vp>raiseAnException_explicit</vp>, so this is the only predicate that needs an implementation. In fact, it is illegal to state clauses for the non-explicit predicate that will never be called.

			There is also a built-in predicate, [[Language Reference/Built-in entities#programPoint\|<vp>programPoint/0-></vp>]], which returns a <vp>programPoint</vp> corresponding to the place where it is called.

	~~The~~ <vp>programPoint</vp> attribute ~~is described in more details~~ in the ~~description of [[Language Reference/Predicates#programPoint\|Predicates]], and it is a vital part of~~ the ~~exception system, see [[Exception Handling]]~~.		To summarize:
			* A predicate declaration with <vp>programPoint</vp> attribute actually declares two predicates. A non-explicit and an explicit predicate.
			* Calling the non-explicit predicate actually results in calling the explicit predicate with the call point as additional argument.
			* Only the explicit predicate should be implemented.

	==== presenter ====		==== presenter ====

Thomas Linder Puls: Undo revision 4876 by Thomas Linder Puls (talk)

2024-01-04T10:31:26Z

Undo revision 4876 by Thomas Linder Puls (talk)

@@ Line 199: / Line 199: @@
 ==== formatString ====
-The argument is a {{lang2|Domains|Format Strings|format string}} for a subsequent ellipsis argument (i.e. <vp>...</vp>).  Valid for one string argument of a predicate with an ellipsis argument.  The use of formatString will make the compiler check the validity of actual arguments with respect to actual format strings (where possible).
+The argument is a format string for a subsequent ellipsis argument (i.e. <vp>...</vp>).  Valid for one string argument of a predicate with an ellipsis argument.  The use of <vp>formatString</vp> will make the compiler check the validity of actual arguments with respect to actual format strings (where possible).
 {{Example|
@@ Line 205: / Line 205: @@
      writef : (string Format [formatString], ...).</vip>
 }}
 ==== generated ====

Thomas Linder Puls: Undo revision 4877 by Thomas Linder Puls (talk)

2024-01-04T10:31:02Z

Undo revision 4877 by Thomas Linder Puls (talk)

Show changes

Thomas Linder Puls: Reverted edits by Thomas Linder Puls (talk) to last revision by Tbn

2024-01-04T10:25:42Z

Reverted edits by Thomas Linder Puls (talk) to last revision by Tbn

Show changes

Thomas Linder Puls: formatString details moved here

2024-01-04T10:23:52Z

formatString details moved here

@@ Line 199: / Line 199: @@
 ==== formatString ====
-The argument is a format string for a subsequent ellipsis argument (i.e. <vp>...</vp>).  Valid for one string argument of a predicate with an ellipsis argument.  The use of <vp>formatString</vp> will make the compiler check the validity of actual arguments with respect to actual format strings (where possible).
+The argument is a {{lang2|Domains|Format Strings|format string}} for a subsequent ellipsis argument (i.e. <vp>...</vp>).  Valid for one string argument of a predicate with an ellipsis argument.  The use of formatString will make the compiler check the validity of actual arguments with respect to actual format strings (where possible).
 {{Example|
@@ Line 205: / Line 205: @@
      writef : (string Format [formatString], ...).</vip>
 }}
 ==== generated ====

Thomas Linder Puls: formatString details moved here

2024-01-04T10:23:42Z

formatString details moved here

@@ Line 199: / Line 199: @@
 ==== formatString ====
-The argument is a {{lang2|Domains|Format Strings|format string}} for a subsequent ellipsis argument (i.e. <vp>...</vp>).  Valid for one string argument of a predicate with an ellipsis argument.  The use of formatString will make the compiler check the validity of actual arguments with respect to actual format strings (where possible).
+The argument is a format string for a subsequent ellipsis argument (i.e. <vp>...</vp>).  Valid for one string argument of a predicate with an ellipsis argument.  The use of <vp>formatString</vp> will make the compiler check the validity of actual arguments with respect to actual format strings (where possible).
 {{Example|
@@ Line 205: / Line 205: @@
      writef : (string Format [formatString], ...).</vip>
 }}
 ==== generated ====

Thomas Linder Puls: explicitTag

2023-10-24T15:25:17Z

explicitTag

@@ Line 182: / Line 182: @@
 <vip>predicates
      oldFashioned : (string Arg) [deprecated("Use newFashion instead")].</vip>
 }}

Thomas Linder Puls: queryable

2023-10-24T15:18:02Z

queryable

← Older revision		Revision as of 17:18, 24 October 2023
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	See [[Presenters]].		See [[Presenters]].

			==== queryable ====

			Makes an entity 'queryable', so that it is available for reflextion using the class <vp>predicateExtractor</vp>.

	==== retired ====		==== retired ====

Thomas Linder Puls: inline prolog predicate type

2021-04-14T09:21:09Z

inline prolog predicate type

← Older revision		Revision as of 11:21, 14 April 2021
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	* inlining a fixed size string		* inlining a fixed size string
	* inlining a fixed number of bytes		* inlining a fixed number of bytes
			* inlining a prolog predicate type (as a struct with two fields)

	When using <vp>inline</vp> on struct field in another struct its data will be inlined instead of having a pointer to the struct		When using <vp>inline</vp> on struct field in another struct its data will be inlined instead of having a pointer to the struct