updates do documentation
put_attrs git-svn-id: https://yap.svn.sf.net/svnroot/yap/trunk@1433 b08c6af1-5177-4d33-ba66-4b1c6b8b522a
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34
C/attvar.c
34
C/attvar.c
@ -451,6 +451,39 @@ p_put_att(void) {
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}
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}
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static Int
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p_put_att_term(void) {
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/* receive a variable in ARG1 */
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Term inp = Deref(ARG1);
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/* if this is unbound, ok */
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if (IsVarTerm(inp)) {
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attvar_record *attv;
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int new = FALSE;
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if (IsAttachedTerm(inp)) {
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attv = (attvar_record *)VarOfTerm(inp);
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} else {
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while (!(attv = BuildNewAttVar())) {
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if (!Yap_growglobal(NULL)) {
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Yap_Error(OUT_OF_ATTVARS_ERROR, ARG1, Yap_ErrorMessage);
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return FALSE;
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}
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inp = Deref(ARG1);
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}
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new = TRUE;
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}
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if (new) {
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attv->Atts = Deref(ARG2);
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} else {
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MaBind(&(attv->Atts), Deref(ARG2));
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}
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return TRUE;
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} else {
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Yap_Error(TYPE_ERROR_VARIABLE,inp,"put_attributes/2");
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return(FALSE);
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}
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}
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static Int
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p_rm_att(void) {
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/* receive a variable in ARG1 */
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@ -890,6 +923,7 @@ void Yap_InitAttVarPreds(void)
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Yap_InitCPred("get_all_swi_atts", 2, p_swi_all_atts, SafePredFlag);
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Yap_InitCPred("free_att", 3, p_free_att, SafePredFlag);
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Yap_InitCPred("put_att", 5, p_put_att, 0);
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Yap_InitCPred("put_att_term", 5, p_put_att_term, 0);
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Yap_InitCPred("put_module_atts", 2, p_put_atts, 0);
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Yap_InitCPred("del_all_module_atts", 2, p_del_atts, 0);
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Yap_InitCPred("rm_att", 4, p_rm_att, 0);
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@ -16,6 +16,7 @@
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<h2>Yap-5.1.0:</h2>
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<ul>
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<li> NEW: put_attrs/2. </li>
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<li> FIXED: don't install CLP unless coroutining && rational trees are
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active. </li>
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<li> FIXED: syntax error in ypp.yap (obs Paulo Moura). </li>
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678
docs/yap.tex
678
docs/yap.tex
@ -8,7 +8,7 @@
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@c @setchapternewpage odd
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@c %**end of header
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@set VERSION: 5.1.0
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@set VERSION 5.1.0
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@set EDITION 4.2.4
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@set UPDATED December 2004
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@ -128,6 +128,7 @@ us to include his text in this document.
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* Modules:: Using Modules in YAP
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* Builtins:: Built In Predicates
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* Library:: Library Predicates
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* SWI-Prolog:: SWI-Prolog emulation
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* Extensions:: Extensions to Standard YAP
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* Rational Trees:: Working with Rational Trees
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* Coroutining:: Changing the Execution of Goals
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@ -234,7 +235,6 @@ Subnodes of Library
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* System:: System Utilities
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* Terms:: Utilities on Terms
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* Cleanup:: Call With registered Cleanup Calls
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* SWI-Prolog:: SWI-Prolog emulation
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* Timeout:: Call With Timeout
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* Trees:: Updatable Binary Trees
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* UGraphs:: Unweighted Graphs
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@ -256,6 +256,12 @@ Subnodes of Attributes
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* Projecting Attributes:: Obtaining the Attributes of Interest
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* Attribute Examples:: Two Simple Examples of how to use Attributes.
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Subnodes of SWI-Prolog
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* Invoking Predicates on all Members of a List :: maplist and friends
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* Forall :: forall builtin
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* hProlog and SWI-Prolog Attributed Variables :: Emulating SWI-like attributed variables
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* SWI-Prolog Global Variables :: Emulating SWI-like attributed variables
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Subnodes of CLP(Q,R)
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* Introduction to CLPQR:: The CLP(Q,R) System
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* Referencing CLPQR:: How to Reference CLP(Q,R)
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@ -306,7 +312,7 @@ Subnodes of C-Interface
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* Yap4 Notes:: Changes in Foreign Predicates Interface
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Subnodes of C-Prolog
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* Major Differences from C-Prolog:: Major Differences between YAP and C-Prolog
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* Major Differences with C-Prolog:: Major Differences between YAP and C-Prolog
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* Fully C-Prolog Compatible:: Yap predicates fully compatible with
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C-Prolog
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* Not Strictly C-Prolog Compatible:: Yap predicates not strictly as C-Prolog
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@ -314,7 +320,7 @@ C-Prolog
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* Not in YAP:: C-Prolog predicates not available in YAP
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Subnodes of SICStus Prolog
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* Major Differences from SICStus:: Major Differences between YAP and SICStus Prolog
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* Major Differences with SICStus:: Major Differences between YAP and SICStus Prolog
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* Fully SICStus Compatible:: Yap predicates fully compatible with
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SICStus Prolog
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* Not Strictly SICStus Compatible:: Yap predicates not strictly as
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@ -6734,7 +6740,7 @@ Stream position at the stream currently being read in.
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@end table
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@node Library, Extensions, Builtins, Top
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@node Library, SWI-Prolog, Builtins, Top
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@chapter Library Predicates
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@ -6762,7 +6768,6 @@ Library, Extensions, Builtins, Top
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* System:: System Utilities
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* Terms:: Utilities on Terms
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* Cleanup:: Call With registered Cleanup Calls
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* SWI-Prolog:: SWI-Prolog emulation
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* Timeout:: Call With Timeout
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* Trees:: Updatable Binary Trees
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* UGraphs:: Unweighted Graphs
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@ -8408,7 +8413,7 @@ term @var{Term}.
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@end table
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@node Cleanup, SWI-Prolog, Cleanup, Library
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@node Cleanup, Timeout, Terms, Library
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@section Call Cleanup
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@cindex cleanup
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@ -8474,134 +8479,7 @@ CleanUpGoals for other than the current cleanup-context.
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Read the Source Luke.
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@node SWI-Prolog, Timeout, SWI-Prolog, Library
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@section SWI-Prolog Emulation
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@cindex SWI-Prolog
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This library provides a number of SWI-Prolog builtins that are not by
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default in YAP. This library is loaded with the
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@code{use_module(library(swi))} command.
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@table @code
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@item append(?@var{List1},?@var{List2},?@var{List3})
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@findex append/3
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@snindex append/3
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@cnindex append/3
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Succeeds when @var{List3} unifies with the concatenation of @var{List1}
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and @var{List2}. The predicate can be used with any instantiation
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pattern (even three variables).
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@item between(+@var{Low},+@var{High},?@var{Value})
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@findex between/3
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@snindex between/3
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@cnindex between/3
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@var{Low} and @var{High} are integers, @var{High} less or equal than
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@var{Low}. If @var{Value} is an integer, $@var{Low} less or equal than
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@var{Value} less or equal than @var{High}$. When @var{Value} is a
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variable it is successively bound to all integers between @var{Low} and
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@var{High}. If @var{High} is @const{inf} @code{between/3| is true iff
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@var{Value} less or equal than @var{Low}, a feature that is particularly
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interesting for generating integers from a certain value.
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@item chdir(+@var{Dir})
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@findex chdir/1
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@snindex chdir/1
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@cnindex chdir/1
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Compatibility predicate. New code should use @code{working_directory/2}.
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@item concat_atom(+@var{List},-@var{Atom})
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@findex concat_atom/2
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@snindex concat_atom/2
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@cnindex concat_atom/2
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@var{List} is a list of atoms, integers or floating point numbers. Succeeds
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if @var{Atom} can be unified with the concatenated elements of @var{List}. If
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@var{List} has exactly 2 elements it is equivalent to @code{atom_concat/3},
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allowing for variables in the list.
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@item concat_atom(?@var{List},+@var{Separator},?@var{Atom})
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@findex concat_atom/3
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@snindex concat_atom/3
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@cnindex concat_atom/3
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Creates an atom just like concat_atom/2, but inserts @var{Separator}
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between each pair of atoms. For example:
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\@example
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?- concat_atom([gnu, gnat], ', ', A).
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A = 'gnu, gnat'
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@end example
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(Unimplemented) This predicate can also be used to split atoms by
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instantiating @var{Separator} and @var{Atom}:
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@example
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?- concat_atom(L, -, 'gnu-gnat').
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L = [gnu, gnat]
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@end example
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@item forall(+@var{Cond},+@var{Action})
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@findex forall/2
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@snindex forall/2
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@cnindex forall/2
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For all alternative bindings of @var{Cond} @var{Action} can be proven.
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The next example verifies that all arithmetic statements in the list
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@var{L} are correct. It does not say which is wrong if one proves wrong.
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@example
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?- forall(member(Result = Formula, [2 = 1 + 1, 4 = 2 * 2]),
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Result =:= Formula).
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@end example
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@item nth1(+@var{Index},?@var{List},?@var{Elem})
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@findex nth1/3
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@snindex nth1/3
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@cnindex nth1/3
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Succeeds when the @var{Index}-th element of @var{List} unifies with
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@var{Elem}. Counting starts at 1.
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Set environment variable. @var{Name} and @var{Value} should be
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instantiated to atoms or integers. The environment variable will be
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passed to @code{shell/[0-2]} and can be requested using @code{getenv/2}.
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They also influence @code{expand_file_name/2}.
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@item setenv(+@var{Name},+@var{Value})
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@findex setenv/2
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@snindex setenv/2
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@cnindex setenv/2
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Set environment variable. @var{Name} and @var{Value} should be
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instantiated to atoms or integers. The environment variable will be
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passed to @code{shell/[0-2]} and can be requested using @code{getenv/2}.
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They also influence @code{expand_file_name/2}.
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@item term_to_atom(?@var{Term},?@var{Atom})
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@findex term_to_atom/2
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@snindex term_to_atom/2
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@cnindex term_to_atom/2
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Succeeds if @var{Atom} describes a term that unifies with @var{Term}. When
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@var{Atom} is instantiated @var{Atom} is converted and then unified with
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@var{Term}. If @var{Atom} has no valid syntax, a @code{syntax_error}
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exception is raised. Otherwise @var{Term} is ``written'' on @var{Atom}
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using @code{write/1}.
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@item working_directory(-@var{Old},+@var{New})
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@findex working_directory/2
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@snindex working_directory/2
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@cnindex working_directory/2
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Unify @var{Old} with an absolute path to the current working directory
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and change working directory to @var{New}. Use the pattern
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@code{working_directory(CWD, CWD)} to get the current directory. See
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also @code{absolute_file_name/2} and @code{chdir/1}.
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@end table
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@node Timeout, Trees, SWI-Prolog, Library
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@node Timeout, Trees, Cleanup, Library
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@section Calls With Timeout
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@cindex timeout
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@ -8611,6 +8489,7 @@ available with the @code{use_module(library(timeout))} command.
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@table @code
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@item time_out(+@var{Goal}, +@var{Timeout}, -@var{Result})
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@findex time_out/3
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@syindex time_out/3
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@ -8936,8 +8815,506 @@ V = [1,3,5]
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@end table
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@node Extensions,Debugging,Library,Top
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@chapter Extensions
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@node SWI-Prolog, Extensions, Library, Top
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@chapter SWI-Prolog Emulation
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@cindex SWI-Prolog
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@menu SWI-Prolog Emulation
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Subnodes of SWI-Prolog
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* Invoking Predicates on all Members of a List :: maplist and friends
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* Forall :: forall builtin
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* hProlog and SWI-Prolog Attributed Variables :: Emulating SWI-like attributed variables
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* SWI-Prolog Global Variables :: Emulating SWI-like attributed variables
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@end menu
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This library provides a number of SWI-Prolog builtins that are not by
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default in YAP. This library is loaded with the
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@code{use_module(library(swi))} command.
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@table @code
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@item append(?@var{List1},?@var{List2},?@var{List3})
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@findex append/3
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@snindex append/3
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@cnindex append/3
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Succeeds when @var{List3} unifies with the concatenation of @var{List1}
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and @var{List2}. The predicate can be used with any instantiation
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pattern (even three variables).
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@item between(+@var{Low},+@var{High},?@var{Value})
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@findex between/3
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@snindex between/3
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@cnindex between/3
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@var{Low} and @var{High} are integers, @var{High} less or equal than
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@var{Low}. If @var{Value} is an integer, @var{Low} less or equal than
|
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@var{Value} less or equal than @var{High}. When @var{Value} is a
|
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variable it is successively bound to all integers between @var{Low} and
|
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@var{High}. If @var{High} is @code{inf}, @code{between/3} is true iff
|
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@var{Value} less or equal than @var{Low}, a feature that is particularly
|
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interesting for generating integers from a certain value.
|
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|
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@item chdir(+@var{Dir})
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@findex chdir/1
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@snindex chdir/1
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@cnindex chdir/1
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|
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Compatibility predicate. New code should use @code{working_directory/2}.
|
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|
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@item concat_atom(+@var{List},-@var{Atom})
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@findex concat_atom/2
|
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@snindex concat_atom/2
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@cnindex concat_atom/2
|
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|
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@var{List} is a list of atoms, integers or floating point numbers. Succeeds
|
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if @var{Atom} can be unified with the concatenated elements of @var{List}. If
|
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@var{List} has exactly 2 elements it is equivalent to @code{atom_concat/3},
|
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allowing for variables in the list.
|
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|
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@item concat_atom(?@var{List},+@var{Separator},?@var{Atom})
|
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@findex concat_atom/3
|
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@snindex concat_atom/3
|
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@cnindex concat_atom/3
|
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|
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Creates an atom just like concat_atom/2, but inserts @var{Separator}
|
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between each pair of atoms. For example:
|
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\@example
|
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?- concat_atom([gnu, gnat], ', ', A).
|
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|
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A = 'gnu, gnat'
|
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@end example
|
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|
||||
(Unimplemented) This predicate can also be used to split atoms by
|
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instantiating @var{Separator} and @var{Atom}:
|
||||
|
||||
@example
|
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?- concat_atom(L, -, 'gnu-gnat').
|
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|
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L = [gnu, gnat]
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@end example
|
||||
|
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@item nth1(+@var{Index},?@var{List},?@var{Elem})
|
||||
@findex nth1/3
|
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@snindex nth1/3
|
||||
@cnindex nth1/3
|
||||
Succeeds when the @var{Index}-th element of @var{List} unifies with
|
||||
@var{Elem}. Counting starts at 1.
|
||||
|
||||
Set environment variable. @var{Name} and @var{Value} should be
|
||||
instantiated to atoms or integers. The environment variable will be
|
||||
passed to @code{shell/[0-2]} and can be requested using @code{getenv/2}.
|
||||
They also influence @code{expand_file_name/2}.
|
||||
|
||||
@item setenv(+@var{Name},+@var{Value})
|
||||
@findex setenv/2
|
||||
@snindex setenv/2
|
||||
@cnindex setenv/2
|
||||
Set environment variable. @var{Name} and @var{Value} should be
|
||||
instantiated to atoms or integers. The environment variable will be
|
||||
passed to @code{shell/[0-2]} and can be requested using @code{getenv/2}.
|
||||
They also influence @code{expand_file_name/2}.
|
||||
|
||||
@item term_to_atom(?@var{Term},?@var{Atom})
|
||||
@findex term_to_atom/2
|
||||
@snindex term_to_atom/2
|
||||
@cnindex term_to_atom/2
|
||||
Succeeds if @var{Atom} describes a term that unifies with @var{Term}. When
|
||||
@var{Atom} is instantiated @var{Atom} is converted and then unified with
|
||||
@var{Term}. If @var{Atom} has no valid syntax, a @code{syntax_error}
|
||||
exception is raised. Otherwise @var{Term} is ``written'' on @var{Atom}
|
||||
using @code{write/1}.
|
||||
|
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@item working_directory(-@var{Old},+@var{New})
|
||||
@findex working_directory/2
|
||||
@snindex working_directory/2
|
||||
@cnindex working_directory/2
|
||||
|
||||
Unify @var{Old} with an absolute path to the current working directory
|
||||
and change working directory to @var{New}. Use the pattern
|
||||
@code{working_directory(CWD, CWD)} to get the current directory. See
|
||||
also @code{absolute_file_name/2} and @code{chdir/1}.
|
||||
|
||||
@end table
|
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|
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@node Invoking Predicates on all Members of a List,Forall, , SWI-Prolog
|
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@section Invoking Predicates on all Members of a List
|
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@c \label{sec:applylist}
|
||||
|
||||
All the predicates in this section call a predicate on all members of a
|
||||
list or until the predicate called fails. The predicate is called via
|
||||
@code{call/[2..]}, which implies common arguments can be put in
|
||||
front of the arguments obtained from the list(s). For example:
|
||||
|
||||
@example
|
||||
?- maplist(plus(1), [0, 1, 2], X).
|
||||
|
||||
X = [1, 2, 3]
|
||||
@end example
|
||||
|
||||
we will phrase this as ``@var{Predicate} is applied on ...''
|
||||
|
||||
@table @code
|
||||
|
||||
@item maplist(+@var{Pred},+@var{List})
|
||||
@findex maplist/2
|
||||
@snindex maplist/2
|
||||
@cnindex maplist/2
|
||||
@var{Pred} is applied successively on each element of @var{List} until
|
||||
the end of the list or @var{Pred} fails. In the latter case
|
||||
@code{maplist/2} fails.
|
||||
|
||||
@item maplist(+@var{Pred},+@var{List1},+@var{List2})
|
||||
@findex maplist/3
|
||||
@snindex maplist/3
|
||||
@cnindex maplist/3
|
||||
Apply @var{Pred} on all successive triples of elements from
|
||||
@var{List1} and
|
||||
@var{List2}. Fails if @var{Pred} can not be applied to a
|
||||
pair. See the example above.
|
||||
|
||||
@item maplist(+@var{Pred},+@var{List1},+@var{List2},+@var{List4})
|
||||
@findex maplist/4
|
||||
@snindex maplist/4
|
||||
@cnindex maplist/4
|
||||
Apply @var{Pred} on all successive triples of elements from @var{List1},
|
||||
@var{List2} and @var{List3}. Fails if @var{Pred} can not be applied to a
|
||||
triple. See the example above.
|
||||
|
||||
@c @item findlist(+@var{Pred},+@var{List1},?@var{List2})
|
||||
@c @findex findlist/3
|
||||
@c @snindex findlist/3
|
||||
@c @cnindex findlist/3
|
||||
@c Unify @var{List2} with a list of all elements of @var{List1} to which
|
||||
@c @var{Pred} applies.
|
||||
@end table
|
||||
|
||||
@node Forall,hProlog and SWI-Prolog Attributed Variables,Invoking Predicates on all Members of a List, SWI-Prolog
|
||||
@section Forall
|
||||
@c \label{sec:forall2}
|
||||
|
||||
@table @code
|
||||
@item forall(+@var{Cond},+@var{Action})
|
||||
@findex forall/2
|
||||
@snindex forall/2
|
||||
@cnindex forall/2
|
||||
|
||||
For all alternative bindings of @var{Cond} @var{Action} can be proven.
|
||||
The next example verifies that all arithmetic statements in the list
|
||||
@var{L} are correct. It does not say which is wrong if one proves wrong.
|
||||
|
||||
@example
|
||||
?- forall(member(Result = Formula, [2 = 1 + 1, 4 = 2 * 2]),
|
||||
Result =:= Formula).
|
||||
@end example
|
||||
|
||||
@end table
|
||||
|
||||
@node hProlog and SWI-Prolog Attributed Variables, SWI-Prolog Global Variables, Forall,SWI-Prolog
|
||||
@section hProlog and SWI-Prolog Attributed Variables
|
||||
@cindex hProlog Attributed Variables
|
||||
|
||||
Attributed variables
|
||||
@c @ref{Attributed variables}
|
||||
provide a technique for extending the
|
||||
Prolog unification algorithm by hooking the binding of attributed
|
||||
variables. There is little consensus in the Prolog community on the
|
||||
exact definition and interface to attributed variables. Yap Prolog
|
||||
traditionally implements a SICStus-like interface, but to enable
|
||||
SWI-compatibility we have implemented the SWI-Prolog interface,
|
||||
identical to the one realised by Bart Demoen for hProlog.
|
||||
|
||||
Binding an attributed variable schedules a goal to be executed at the
|
||||
first possible opportunity. In the current implementation the hooks are
|
||||
executed immediately after a successful unification of the clause-head
|
||||
or successful completion of a foreign language (builtin) predicate. Each
|
||||
attribute is associated to a module and the hook (attr_unify_hook/2) is
|
||||
executed in this module. The example below realises a very simple and
|
||||
incomplete finite domain reasoner.
|
||||
|
||||
@example
|
||||
:- module(domain,
|
||||
[ domain/2 % Var, ?Domain
|
||||
]).
|
||||
:- use_module(library(oset)).
|
||||
|
||||
domain(X, Dom) :-
|
||||
var(Dom), !,
|
||||
get_attr(X, domain, Dom).
|
||||
domain(X, List) :-
|
||||
sort(List, Domain),
|
||||
put_attr(Y, domain, Domain),
|
||||
X = Y.
|
||||
|
||||
% An attributed variable with attribute value Domain has been
|
||||
% assigned the value Y
|
||||
|
||||
attr_unify_hook(Domain, Y) :-
|
||||
( get_attr(Y, domain, Dom2)
|
||||
-> oset_int(Domain, Dom2, NewDomain),
|
||||
( NewDomain == []
|
||||
-> fail
|
||||
; NewDomain = [Value]
|
||||
-> Y = Value
|
||||
; put_attr(Y, domain, NewDomain)
|
||||
)
|
||||
; var(Y)
|
||||
-> put_attr( Y, domain, Domain )
|
||||
; memberchk(Y, Domain)
|
||||
).
|
||||
@end example
|
||||
|
||||
|
||||
Before explaining the code we give some example queries:
|
||||
|
||||
@table @code
|
||||
@item ?- domain(X, [a,b]), X = c
|
||||
no
|
||||
@item ?- domain(X, [a,b]), domain(X, [a,c]).
|
||||
X = a
|
||||
@item ?- domain(X, [a,b,c]), domain(X, [a,c]).
|
||||
X = _D0
|
||||
@end table
|
||||
|
||||
The predicate @code{domain/2} fetches (first clause) or assigns
|
||||
(second clause) the variable a @emph{domain}, a set of values it can
|
||||
be unified with. In the second clause first associates the domain
|
||||
with a fresh variable and then unifies X to this variable to deal
|
||||
with the possibility that X already has a domain. The
|
||||
predicate @code{attr_unify_hook/2} is a hook called after a variable with
|
||||
a domain is assigned a value. In the simple case where the variable
|
||||
is bound to a concrete value we simply check whether this value is in
|
||||
the domain. Otherwise we take the intersection of the domains and either
|
||||
fail if the intersection is empty (first example), simply assign the
|
||||
value if there is only one value in the intersection (second example) or
|
||||
assign the intersection as the new domain of the variable (third
|
||||
example).
|
||||
|
||||
|
||||
@table @code
|
||||
|
||||
@item put_attr(+@var{Var},+@var{Module},+@var{Value})
|
||||
@findex put_attr/3
|
||||
@snindex put_attr/3
|
||||
@cnindex put_attr/3
|
||||
If @var{Var} is a variable or attributed variable, set the value for the
|
||||
attribute named @var{Module} to @var{Value}. If an attribute with this
|
||||
name is already associated with @var{Var}, the old value is replaced.
|
||||
Backtracking will restore the old value (i.e. an attribute is a mutable
|
||||
term. See also @code{setarg/3}). This predicate raises a type error if
|
||||
@var{Var} is not a variable or @var{Module} is not an atom.
|
||||
|
||||
@item get_attr(+@var{Var},+@var{Module},+@var{Value})
|
||||
@findex get_attr/3
|
||||
@snindex get_attr/3
|
||||
@cnindex get_attr/3
|
||||
Request the current @var{value} for the attribute named @var{Module}. If
|
||||
@var{Var} is not an attributed variable or the named attribute is not
|
||||
associated to @var{Var} this predicate fails silently. If @var{Module}
|
||||
is not an atom, a type error is raised.
|
||||
|
||||
@item del_attr(+@var{Var},+@var{Module})
|
||||
@findex del_attr/2
|
||||
@snindex del_attr/2
|
||||
@cnindex del_attr/2
|
||||
Delete the named attribute. If @var{Var} loses its last attribute it
|
||||
is transformed back into a traditional Prolog variable. If @var{Module}
|
||||
is not an atom, a type error is raised. In all other cases this
|
||||
predicate succeeds regarless whether or not the named attribute is
|
||||
present.
|
||||
|
||||
@item attr_unify_hook(+@var{AttValue},+@var{VarValue})
|
||||
@findex attr_unify_hook/2
|
||||
@snindex attr_unify_hook/2
|
||||
@cnindex attr_unify_hook/2
|
||||
Hook that must be defined in the module an attributed variable refers
|
||||
to. Is is called @emph{after} the attributed variable has been
|
||||
unified with a non-var term, possibly another attributed variable.
|
||||
@var{AttValue} is the attribute that was associated to the variable
|
||||
in this module and @var{VarValue} is the new value of the variable.
|
||||
Normally this predicate fails to veto binding the variable to
|
||||
@var{VarValue}, forcing backtracking to undo the binding. If
|
||||
@var{VarValue} is another attributed variable the hook often combines
|
||||
the two attribute and associates the combined attribute with
|
||||
@var{VarValue} using @code{put_attr/3}.
|
||||
|
||||
@c \predicate{attr_portray_hook}{2}{+AttValue, +Var}
|
||||
@c Called by write_term/2 and friends for each attribute if the option
|
||||
@c \term{attributes}{portray} is in effect. If the hook succeeds the
|
||||
@c attribute is considered printed. Otherwise \exam{Module = ...} is
|
||||
@c printed to indicate the existence of a variable.
|
||||
@end table
|
||||
|
||||
@subsection Special Purpose SWI Predicates for Attributes
|
||||
|
||||
Normal user code should deal with @code{put_attr/3}, @code{get_attr/3}
|
||||
and @code{del_attr/2}. The routines in this section fetch or set the
|
||||
entire attribute list of a variables. Use of these predicates is
|
||||
anticipated to be restricted to printing and other special purpose
|
||||
operations.
|
||||
|
||||
@table @code
|
||||
@item get_attrs(+@var{Var},-@var{Attributes})
|
||||
@findex get_attrs/2
|
||||
@snindex get_attrs/2
|
||||
@cnindex get_attrs/2
|
||||
Get all attributes of @var{Var}. @var{Attributes} is a term of the form
|
||||
@code{att(Module, Value, MoreAttributes)}, where @var{MoreAttributes} is
|
||||
@code{[]} for the last attribute.
|
||||
|
||||
@item put_attrs(+@var{Var},+@var{Attributes})
|
||||
@findex put_attrs/2
|
||||
@snindex put_attrs/2
|
||||
@cnindex put_attrs/2
|
||||
Set all attributes of @var{Var}. See get_attrs/2 for a description of
|
||||
@var{Attributes}.
|
||||
|
||||
@item copy_term_nat(?@var{TI},-@var{TF})
|
||||
@findex copy_term_nat/2
|
||||
@snindex copy_term_nat/2
|
||||
@cnindex copy_term_nat/2
|
||||
As @code{copy_term/2}. Attributes however, are @emph{not} copied but replaced
|
||||
by fresh variables.
|
||||
@end table
|
||||
|
||||
|
||||
@node SWI-Prolog Global Variables, ,hProlog and SWI-Prolog Attributed Variables,SWI-Prolog
|
||||
@section SWI Global variables
|
||||
@c \label{sec:gvar}
|
||||
|
||||
SWI-Prolog global variables are associations between names (atoms) and
|
||||
terms. They differ in various ways from storing information using
|
||||
@code{assert/1} or @code{recorda/3}.
|
||||
|
||||
@itemize @bullet
|
||||
@item The value lives on the Prolog (global) stack. This implies
|
||||
that lookup time is independent from the size of the term.
|
||||
This is particulary interesting for large data structures
|
||||
such as parsed XML documents or the CHR global constraint
|
||||
store.
|
||||
|
||||
@item They support both global assignment using @code{nb_setval/2} and
|
||||
backtrackable assignment using @code{b_setval/2}.
|
||||
|
||||
@item Only one value (which can be an arbitrary complex Prolog
|
||||
term) can be associated to a variable at a time.
|
||||
|
||||
@item Their value cannot be shared among threads. Each thread
|
||||
has its own namespace and values for global variables.
|
||||
|
||||
@item Currently global variables are scoped globally. We may
|
||||
consider module scoping in future versions.
|
||||
@end itemize
|
||||
|
||||
Both @code{b_setval/2} and @code{nb_setval/2} implicitely create a variable if the
|
||||
referenced name does not already refer to a variable.
|
||||
|
||||
Global variables may be initialised from directives to make them
|
||||
available during the program lifetime, but some considerations are
|
||||
necessary for saved-states and threads. Saved-states to not store global
|
||||
variables, which implies they have to be declared with @code{initialization/1}
|
||||
to recreate them after loading the saved state. Each thread has
|
||||
its own set of global variables, starting with an empty set. Using
|
||||
@code{thread_inititialization/1} to define a global variable it will be
|
||||
defined, restored after reloading a saved state and created in all
|
||||
threads that are created @emph{after} the registration.
|
||||
|
||||
|
||||
@table @code
|
||||
@item b_setval(+@var{Name},+@var{Value})
|
||||
@findex b_setval/2
|
||||
@snindex b_setval/2
|
||||
@cnindex b_setval/2
|
||||
Associate the term @var{Value} with the atom @var{Name} or replaces
|
||||
the currently associated value with @var{Value}. If @var{Name} does
|
||||
not refer to an existing global variable a variable with initial value
|
||||
@code{[]} is created (the empty list). On backtracking the
|
||||
assignment is reversed.
|
||||
|
||||
@item b_getval(+@var{Name},-@var{Value})
|
||||
@findex b_getval/2
|
||||
@snindex b_getval/2
|
||||
@cnindex b_getval/2
|
||||
Get the value associated with the global variable @var{Name} and unify
|
||||
it with @var{Value}. Note that this unification may further instantiate
|
||||
the value of the global variable. If this is undesirable the normal
|
||||
precautions (double negation or @code{copy_term/2}) must be taken. The
|
||||
@code{b_getval/2} predicate generates errors if @var{Name} is not an atom or
|
||||
the requested variable does not exist.
|
||||
@end table
|
||||
|
||||
@table @code
|
||||
|
||||
@item nb_setval(+@var{Name},+@var{Value})
|
||||
@findex nb_setval/2
|
||||
@snindex nb_setval/2
|
||||
@cnindex nb_setval/2
|
||||
Associates a copy of @var{Value} created with @code{duplicate_term/2}
|
||||
with the atom @var{Name}. Note that this can be used to set an
|
||||
initial value other than @code{[]} prior to backtrackable assignment.
|
||||
|
||||
@item nb_getval(+@var{Name},-@var{Value})
|
||||
@findex nb_getval/2
|
||||
@snindex nb_getval/2
|
||||
@cnindex nb_getval/2
|
||||
The @code{nb_getval/2} predicate is a synonym for b_getval/2, introduced for
|
||||
compatibility and symetry. As most scenarios will use a particular
|
||||
global variable either using non-backtracable or backtrackable
|
||||
assignment, using @code{nb_getval/2} can be used to document that the
|
||||
variable is used non-backtracable.
|
||||
|
||||
@c \predicate{nb_linkval}{2}{+Name, +Value}
|
||||
@c Associates the term @var{Value} with the atom @var{Name} without copying
|
||||
@c it. This is a fast special-purpose variation of nb_setval/2 intended for
|
||||
@c expert users only because the semantics on backtracking to a point
|
||||
@c before creating the link are poorly defined for compound terms. The
|
||||
@c principal term is always left untouched, but backtracking behaviour on
|
||||
@c arguments is undone if the orginal assignment was \jargon{trailed} and
|
||||
@c left alone otherwise, which implies that the history that created the
|
||||
@c term affects the behaviour on backtracking. Please consider the
|
||||
@c following example:
|
||||
|
||||
@c \begin{code}
|
||||
@c demo_nb_linkval :-
|
||||
@c T = nice(N),
|
||||
@c ( N = world,
|
||||
@c nb_linkval(myvar, T),
|
||||
@c fail
|
||||
@c ; nb_getval(myvar, V),
|
||||
@c writeln(V)
|
||||
@c ).
|
||||
@c \end{code}
|
||||
|
||||
@item nb_current(?@var{Name},?@var{Value})
|
||||
@findex nb_current/2
|
||||
@snindex nb_current/2
|
||||
@cnindex nb_current/2
|
||||
Enumerate all defined variables with their value. The order of
|
||||
enumeration is undefined.
|
||||
|
||||
@item nb_delete(?@var{Name})
|
||||
@findex nb_delete/1
|
||||
@snindex nb_delete/1
|
||||
@cnindex nb_delete/1
|
||||
Delete the named global variable.
|
||||
@end table
|
||||
|
||||
@subsection Compatibility of SWI-Prolog Global Variables
|
||||
|
||||
Global variables have been introduced by various Prolog
|
||||
implementations recently. The implementation of them in SWI-Prolog is
|
||||
based on hProlog by Bart Demoen. In discussion with Bart it was
|
||||
decided that the semantics if hProlog @code{nb_setval/2}, which is
|
||||
equivalent to @code{nb_linkval/2} is not acceptable for normal Prolog
|
||||
users as the behaviour is influenced by how builtin predicates
|
||||
constructing terms (@code{read/1}, @code{=../2}, etc.) are implemented.
|
||||
|
||||
GNU-Prolog provides a rich set of global variables, including arrays.
|
||||
Arrays can be implemented easily in SWI-Prolog using @code{functor/3} and
|
||||
@code{setarg/3} due to the unrestricted arity of compound terms.
|
||||
|
||||
|
||||
@node Extensions,Debugging,SWI-Prolog,Top
|
||||
@chapter Extensions to Prolog
|
||||
|
||||
YAP includes several extensions that are not enabled by
|
||||
default, but that can be used to extend the functionality of the
|
||||
@ -8945,7 +9322,6 @@ system. These options can be set at compilation time by enabling the
|
||||
related compilation flag, as explained in the @code{Makefile}
|
||||
|
||||
@menu
|
||||
|
||||
Extensions to Traditional Prolog
|
||||
|
||||
* Rational Trees:: Working with Rational Trees
|
||||
@ -8961,7 +9337,7 @@ Extensions to Traditional Prolog
|
||||
@end menu
|
||||
|
||||
@node Rational Trees, Coroutining, , Extensions
|
||||
@chapter Rational Trees
|
||||
@section Rational Trees
|
||||
|
||||
Prolog unification is not a complete implementation. For efficiency
|
||||
considerations, Prolog systems do not perform occur checks while
|
||||
@ -8969,9 +9345,10 @@ unifying terms. As an example, @code{X = a(X)} will not fail but instead
|
||||
will create an infinite term of the form @code{a(a(a(a(a(...)))))}, or
|
||||
@emph{rational tree}.
|
||||
|
||||
By default, rational trees are not supported in YAP, and these
|
||||
terms can easily lead to infinite computation. For example, @code{X =
|
||||
a(X), X = X} will enter an infinite loop.
|
||||
Rational trees are no supported by default in YAP. In previous
|
||||
versions, this was not the default and these terms could easily lead
|
||||
to infinite computation. For example, @code{X = a(X), X = X} would
|
||||
enter an infinite loop.
|
||||
|
||||
The @code{RATIONAL_TREES} flag improves support for these
|
||||
terms. Internal primitives are now aware that these terms can exist, and
|
||||
@ -8985,7 +9362,7 @@ rational trees, and you need to use @code{write_depth/2} to avoid
|
||||
entering an infinite cycle when trying to write an infinite term.
|
||||
|
||||
@node Coroutining, Attributed Variables, Rational Trees, Extensions
|
||||
@chapter Coroutining
|
||||
@section Coroutining
|
||||
|
||||
Prolog uses a simple left-to-right flow of control. It is sometimes
|
||||
convenient to change this control so that goals will only be executed
|
||||
@ -9088,7 +9465,6 @@ suspended.
|
||||
|
||||
@end table
|
||||
|
||||
|
||||
@node Attributed Variables, CLPQR, Coroutining, Extensions
|
||||
@chapter Attributed Variables
|
||||
@cindex attributed variables
|
||||
@ -14078,9 +14454,9 @@ would have something like
|
||||
@example
|
||||
void
|
||||
init_n100(void)
|
||||
{
|
||||
@{
|
||||
YAP_UserBackCPredicate("n100", start_n100, continue_n100, 1, 1);
|
||||
}
|
||||
@}
|
||||
@end example
|
||||
|
||||
|
||||
@ -14449,7 +14825,7 @@ YAP compatible with the ISO-Prolog standard.
|
||||
|
||||
@menu
|
||||
C-Prolog Compatibility
|
||||
* Major Differences from C-Prolog:: Major Differences between YAP and C-Prolog
|
||||
* Major Differences with C-Prolog:: Major Differences between YAP and C-Prolog
|
||||
* Fully C-Prolog Compatible:: Yap predicates fully compatible with
|
||||
C-Prolog
|
||||
* Not Strictly C-Prolog Compatible:: Yap predicates not strictly as C-Prolog
|
||||
@ -14457,7 +14833,7 @@ C-Prolog
|
||||
* Not in YAP:: C-Prolog predicates not available in YAP
|
||||
@end menu
|
||||
|
||||
@node Major Differences from C-Prolog, Fully C-Prolog Compatible, , C-Prolog
|
||||
@node Major Differences with C-Prolog, Fully C-Prolog Compatible, , C-Prolog
|
||||
@subsection Major Differences between YAP and C-Prolog.
|
||||
|
||||
YAP includes several extensions over the original C-Prolog system. Even
|
||||
@ -14496,7 +14872,7 @@ or by using:
|
||||
@code{:- yap_flag(language,cprolog).}
|
||||
@end example
|
||||
|
||||
@node Fully C-Prolog Compatible, Not Strictly C-Prolog Compatible, Major Differences from C-Prolog, C-Prolog
|
||||
@node Fully C-Prolog Compatible, Not Strictly C-Prolog Compatible, Major Differences with C-Prolog, C-Prolog
|
||||
@subsection Yap predicates fully compatible with C-Prolog
|
||||
|
||||
These are the Prolog built-ins that are fully compatible in both
|
||||
@ -14559,7 +14935,7 @@ for maximum compatibility with SICStus Prolog.
|
||||
|
||||
@menu
|
||||
SICStus Compatibility
|
||||
* Major Differences from SICStus:: Major Differences between YAP and SICStus Prolog
|
||||
* Major Differences with SICStus:: Major Differences between YAP and SICStus Prolog
|
||||
* Fully SICStus Compatible:: Yap predicates fully compatible with
|
||||
SICStus Prolog
|
||||
* Not Strictly SICStus Compatible:: Yap predicates not strictly as
|
||||
@ -14567,7 +14943,7 @@ SICStus Prolog
|
||||
* Not in SICstus Prolog:: Yap predicates not available in SICStus Prolog
|
||||
@end menu
|
||||
|
||||
@node Major Differences from SICStus, Fully SICStus Compatible, , SICStus Prolog
|
||||
@node Major Differences with SICStus, Fully SICStus Compatible, , SICStus Prolog
|
||||
@subsection Major Differences between YAP and SICStus Prolog.
|
||||
|
||||
Both YAP and SICStus Prolog obey the Edinburgh Syntax and are based on
|
||||
|
||||
@ -152,9 +152,14 @@ prolog:get_attrs(AttVar, SWIAtts) :-
|
||||
get_all_swi_atts(AttVar,SWIAtts).
|
||||
|
||||
prolog:put_attrs(_, []).
|
||||
prolog:put_attrs(V, att(Mod,Att,Atts)) :-
|
||||
prolog:put_attr(V,Mod,Att),
|
||||
prolog:put_attrs(V, Atts).
|
||||
prolog:put_attrs(V, Atts) :-
|
||||
cvt_to_swi_atts(Atts, YapAtts),
|
||||
attributes:put_att_term(V, YapAtts).
|
||||
|
||||
cvt_to_swi_atts([], _).
|
||||
cvt_to_swi_atts(att(Mod,Attribute,Atts), ModAttribute) :-
|
||||
ModAttribute =.. [Mod, YapAtts, Attribute],
|
||||
cvt_to_swi_atts(Atts, YapAtts).
|
||||
|
||||
bindings_message(V) -->
|
||||
{ cvt_bindings(V, Bindings) },
|
||||
|
||||
Reference in New Issue
Block a user