3.21.5 Examples for using the HTML write library
In the following example we will generate a table of Prolog predicates we find from the SWI-Prolog help system based on a keyword. The primary database is defined by the predicate predicate/5 We will make hyperlinks for the predicates pointing to their documentation.
html_apropos(Kwd) :- findall(Pred, apropos_predicate(Kwd, Pred), Matches), phrase(apropos_page(Kwd, Matches), Tokens), print_html(Tokens). % emit page with title, header and table of matches apropos_page(Kwd, Matches) --> page([ title(['Predicates for ', Kwd]) ], [ h2(align(center), ['Predicates for ', Kwd]), table([ align(center), border(1), width('80%') ], [ tr([ th('Predicate'), th('Summary') ]) | \apropos_rows(Matches) ]) ]). % emit the rows for the body of the table. apropos_rows([]) --> []. apropos_rows([pred(Name, Arity, Summary)|T]) --> html([ tr([ td(\predref(Name/Arity)), td(em(Summary)) ]) ]), apropos_rows(T). % predref(Name/Arity) % % Emit Name/Arity as a hyperlink to % % /cgi-bin/plman?name=Name&arity=Arity % % we must do form-encoding for the name as it may contain illegal % characters. www_form_encode/2 is defined in library(url). predref(Name/Arity) --> { www_form_encode(Name, Encoded), sformat(Href, '/cgi-bin/plman?name=~w&arity=~w', [Encoded, Arity]) }, html(a(href(Href), [Name, /, Arity])). % Find predicates from a keyword. '$apropos_match' is an internal % undocumented predicate. apropos_predicate(Pattern, pred(Name, Arity, Summary)) :- predicate(Name, Arity, Summary, _, _), ( '$apropos_match'(Pattern, Name) -> true ; '$apropos_match'(Pattern, Summary) ).