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Variable naming/numbering
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<TR><TD><FONT SIZE=4><B><A NAME="htoc82">7.5</A></B></FONT></TD>
<TD WIDTH="100%" ALIGN=center><FONT SIZE=4><B>Variable naming/numbering</B></FONT></TD>
</TR></TABLE></DIV></TD>
</TR></TABLE><UL>
<LI><A HREF="manual028.html#toc56"> <TT>name_singleton_vars/1</TT></A>
<LI><A HREF="manual028.html#toc57"> <TT>name_query_vars/2</TT></A>
<LI><A HREF="manual028.html#toc58"> <TT>bind_variables/2</TT>,
<TT>numbervars/3</TT>,
<TT>numbervars/1</TT></A>
<LI><A HREF="manual028.html#toc59"> <TT>term_ref/2</TT></A>
</UL>
<A NAME="Variable-naming/numbering"></A><BR>
<A NAME="toc56"></A><TABLE CELLPADDING=0 CELLSPACING=0 WIDTH="100%">
<TR><TD BGCOLOR="#98e7ff"><DIV ALIGN=center><TABLE>
<TR><TD><B><A NAME="htoc83">7.5.1</A></B></TD>
<TD WIDTH="100%" ALIGN=center><TT><B>name_singleton_vars/1</B></TT></TD>
</TR></TABLE></DIV></TD>
</TR></TABLE>
<A NAME="name-singleton-vars/1"></A>
<BR>
<B>Templates</B>
<DL COMPACT=compact><DT><DD><TT>
name_singleton_vars(?term)</TT></DL>
<B>Description</B><BR>
<BR>
<TT>name_singleton_vars(Term)</TT> binds each singleton variable appearing
in <TT>Term</TT> with a term of the form <TT>'$VARNAME'('_')</TT>. Such a
term can be output by <TT>write_term/3</TT> as a variable name
(section <A HREF="manual037.html#write-term/3">7.14.6</A>).<BR>
<BR>
<B>Errors</B><BR>
<BR>
None.<BR>
<BR>
<B>Portability</B><BR>
<BR>
GNU Prolog predicates.<BR>
<BR>
<A NAME="toc57"></A><TABLE CELLPADDING=0 CELLSPACING=0 WIDTH="100%">
<TR><TD BGCOLOR="#98e7ff"><DIV ALIGN=center><TABLE>
<TR><TD><B><A NAME="htoc84">7.5.2</A></B></TD>
<TD WIDTH="100%" ALIGN=center><TT><B>name_query_vars/2</B></TT></TD>
</TR></TABLE></DIV></TD>
</TR></TABLE>
<A NAME="name-query-vars/2"></A>
<BR>
<B>Templates</B>
<DL COMPACT=compact><DT><DD><TT>
name_query_vars(+list, ?list)</TT></DL>
<B>Description</B><BR>
<BR>
<TT>name_query_vars(List, Rest)</TT> for each element of <TT>List</TT> of
the form <TT>Name = Var</TT> where <TT>Name</TT> is an atom and <TT>Var</TT>
a variable, binds <TT>Var</TT> with the term <TT>'$VARNAME'(Name)</TT>.
Such a term can be output by <TT>write_term/3</TT> as a variable name
(section <A HREF="manual037.html#write-term/3">7.14.6</A>). <TT>Rest</TT> is unified with the list of elements of
<TT>List</TT> that have not given rise to a binding. This predicate is
provided as a way to name the variable lists obtained returned by
<TT>read_term/3</TT> with <TT>variable_names(List)</TT> or
<TT>singletons(List)</TT> options (section <A HREF="manual037.html#read-term/3">7.14.1</A>).<BR>
<BR>
<B>Errors</B><BR>
<TABLE CELLSPACING=2 CELLPADDING=0>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>List</TT> is a partial list</TD>
<TD VALIGN=top ALIGN=center NOWRAP> </TD>
<TD VALIGN=top ALIGN=left><TT>instantiation_error</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>List</TT> is neither a partial list nor a list</TD>
<TD VALIGN=top ALIGN=center NOWRAP> </TD>
<TD VALIGN=top ALIGN=left><TT>type_error(list, List)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Rest</TT> is neither a partial list nor a list</TD>
<TD VALIGN=top ALIGN=center NOWRAP> </TD>
<TD VALIGN=top ALIGN=left><TT>type_error(list, Rest)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR></TABLE><BR>
<B>Portability</B><BR>
<BR>
GNU Prolog predicate.<BR>
<BR>
<A NAME="toc58"></A><TABLE CELLPADDING=0 CELLSPACING=0 WIDTH="100%">
<TR><TD BGCOLOR="#98e7ff"><DIV ALIGN=center><TABLE>
<TR><TD><B><A NAME="htoc85">7.5.3</A></B></TD>
<TD WIDTH="100%" ALIGN=center><B><TT>bind_variables/2</TT>,
<TT>numbervars/3</TT>,
<TT>numbervars/1</TT></B></TD>
</TR></TABLE></DIV></TD>
</TR></TABLE>
<A NAME="bind-variables/2"></A>
<BR>
<B>Templates</B>
<DL COMPACT=compact><DT><DD><TT>
bind_variables(?term, +var_binding_option_list)<BR>
numbervars(?term, +integer, ?integer)<BR>
numbervars(?term)</TT></DL>
<B>Description</B><BR>
<BR>
<TT>bind_variables(Term, Options)</TT> binds each variable appearing in
<TT>Term</TT> according to the options given by <TT>Options</TT>. <BR>
<BR>
<B>Variable binding options</B>: <TT>Options</TT> is a list of variable
binding options. If this list contains contradictory options, the rightmost
option is the one which applies. Possible options are:
<UL><LI><TT>numbervars</TT>: specifies that each variable appearing in
<TT>Term</TT> should be bound to a term of the form <TT>'$VAR'(N)</TT>
where <TT>N</TT> is an integer. Such a term can be output by
<TT>write_term/3</TT> as a variable name (section <A HREF="manual037.html#write-term/3">7.14.6</A>). This is
the default.<BR>
<BR>
<LI><TT>namevars</TT>: specifies that each variables appearing in
<TT>Term</TT> shall be bound to a term of the form
<TT>'$VARNAME'(Name)</TT> where <TT>Name</TT> is the atom that would be
output by <TT>write_term/3</TT> seeing a term of the <TT>'$VAR'(N)</TT>
where <TT>N</TT> is an integer. Such a term can be output by
<TT>write_term/3</TT> as a variable name (section <A HREF="manual037.html#write-term/3">7.14.6</A>). This is
the alternative to <TT>numbervars</TT>.<BR>
<BR>
<LI><TT>from(From)</TT>: the first integer <TT>N</TT> to use for
number/name variables of <TT>Term</TT> is <TT>From</TT>. The default value
is <TT>0</TT>.<BR>
<BR>
<LI><TT>next(Next)</TT>: when <TT>bind_variables/2</TT> succeeds,
<TT>Next</TT> is unified with the (last integer <TT>N</TT>)+1 used
to bind the variables of <TT>Term</TT>. <BR>
<BR>
<LI><TT>exclude(List)</TT>: collects all variable names appearing
in <TT>List</TT> to avoid a clash when binding a variable of <TT>Term</TT>.
Precisely a number <TT>N</TT> >= <TT>From</TT> will not be used to bind a
variable of <TT>Term</TT> if:
<UL><LI>there is a sub-term of <TT>List</TT> of the form <TT>'$VAR'(N)</TT>
or <TT>'$VARNAME'(Name)</TT> where <TT>Name</TT> is the constant that would
be output by <TT>write_term/3</TT> seeing a term of the
<TT>'$VAR'(N)</TT>.<BR>
<BR>
<LI>an element of <TT>List</TT> is of the form <TT>Name = Var</TT> where
<TT>Name</TT> is an atom that would be output by <TT>write_term/3</TT> on
seeing a term of the from <TT>'$VAR'(N)</TT>. This case allows for lists
returned by <TT>read_term/3</TT>
(with <TT>variable_names(List)</TT> or
<TT>singletons(List)</TT> options) (section <A HREF="manual037.html#read-term/3">7.14.1</A>) and by
<TT>name_query_vars/2</TT> (section <A HREF="#name-query-vars/2">7.5.2</A>).</UL></UL>
<TT>numbervars(Term, From, Next)</TT> is equivalent to
<TT>bind_variables(Term, [from(From), next(Next)]</TT>, i.e. each variable
of <TT>Term</TT> is bound to <TT>'$VAR'(N)</TT> where <TT>From <=</TT>
<TT>N</TT> < <TT>Next</TT>.<BR>
<BR>
<TT>numbervars(Term)</TT> is equivalent to <TT>numbervars(Term, 0, _)</TT>.<BR>
<BR>
<B>Errors</B><BR>
<TABLE CELLSPACING=2 CELLPADDING=0>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Options</TT> is a partial list or a list with an element
<TT>E</TT> which is a variable</TD>
<TD VALIGN=top ALIGN=center NOWRAP> </TD>
<TD VALIGN=top ALIGN=left><TT>instantiation_error</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Options</TT> is neither a partial list nor a list</TD>
<TD VALIGN=top ALIGN=center NOWRAP> </TD>
<TD VALIGN=top ALIGN=left><TT>type_error(list, Options)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left>an element <TT>E</TT> of the <TT>Options</TT> list is neither a
variable nor a variable binding option</TD>
<TD VALIGN=top ALIGN=center NOWRAP> </TD>
<TD VALIGN=top ALIGN=left><TT>domain_error(var_binding_option, E)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>From</TT> is a variable</TD>
<TD VALIGN=top ALIGN=center NOWRAP> </TD>
<TD VALIGN=top ALIGN=left><TT>instantiation_error</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>From</TT> is neither a variable nor an integer</TD>
<TD VALIGN=top ALIGN=center NOWRAP> </TD>
<TD VALIGN=top ALIGN=left><TT>type_error(integer, From)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Next</TT> is neither a variable nor an integer</TD>
<TD VALIGN=top ALIGN=center NOWRAP> </TD>
<TD VALIGN=top ALIGN=left><TT>type_error(integer, Next)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>List</TT> is a partial list</TD>
<TD VALIGN=top ALIGN=center NOWRAP> </TD>
<TD VALIGN=top ALIGN=left><TT>instantiation_error</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>List</TT> is neither a partial list nor a list</TD>
<TD VALIGN=top ALIGN=center NOWRAP> </TD>
<TD VALIGN=top ALIGN=left><TT>type_error(list, List)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR></TABLE><BR>
<B>Portability</B><BR>
<BR>
GNU Prolog predicates.<BR>
<BR>
<A NAME="toc59"></A><TABLE CELLPADDING=0 CELLSPACING=0 WIDTH="100%">
<TR><TD BGCOLOR="#98e7ff"><DIV ALIGN=center><TABLE>
<TR><TD><B><A NAME="htoc86">7.5.4</A></B></TD>
<TD WIDTH="100%" ALIGN=center><TT><B>term_ref/2</B></TT></TD>
</TR></TABLE></DIV></TD>
</TR></TABLE>
<BR>
<B>Templates</B>
<DL COMPACT=compact><DT><DD><TT>
term_ref(+term, ?integer)<BR>
term_ref(?term, +integer)</TT></DL>
<B>Description</B><BR>
<BR>
<TT>term_ref(Term, Ref)</TT> succeeds if the internal reference of
<TT>Term</TT> is <TT>Ref</TT>. This predicate can be used either to obtain
the internal reference of a term or to obtain the term associated to a given
reference. Note that two identical terms can have different internal
references. A good way to use this predicate is to first record the internal
reference of a given term and to later re-obtain the term via this
reference.<BR>
<BR>
<B>Errors</B><BR>
<TABLE CELLSPACING=2 CELLPADDING=0>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Term</TT> and <TT>Ref</TT> are both variables</TD>
<TD VALIGN=top ALIGN=center NOWRAP> </TD>
<TD VALIGN=top ALIGN=left><TT>instantiation_error</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Ref</TT> is neither a variable nor an integer</TD>
<TD VALIGN=top ALIGN=center NOWRAP> </TD>
<TD VALIGN=top ALIGN=left><TT>type_error(integer, Ref)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Ref</TT> is an integer < 0</TD>
<TD VALIGN=top ALIGN=center NOWRAP> </TD>
<TD VALIGN=top ALIGN=left><TT>domain_error(not_less_than_zero, Ref)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR></TABLE><BR>
<B>Portability</B><BR>
<BR>
GNU Prolog predicate.<BR>
<BR>
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Copyright (C) 1999-2002 Daniel Diaz
<BR>
<BR>
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