remove vestigial prolog/ directory (#444)
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Mark Thom
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src/lib/tabling/table_link_manager.pl
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123
src/lib/tabling/table_link_manager.pl
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/* Part of SWI-Prolog
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Author: Benoit Desouter <Benoit.Desouter@UGent.be>
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Jan Wielemaker (SWI-Prolog port)
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Copyright (c) 2016, Benoit Desouter
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All rights reserved.
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Ported to Scryer Prolog by Mark Thom (2019/2020).
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions
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are met:
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1. Redistributions of source code must retain the above copyright
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notice, this list of conditions and the following disclaimer.
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2. Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions and the following disclaimer in
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the documentation and/or other materials provided with the
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distribution.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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POSSIBILITY OF SUCH DAMAGE.
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*/
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:- module(table_link_manager,
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[ get_existing_tables/1, % -Tables
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p_existing_table/2, % +Variant, -TableID
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p_link_variant_identifier/2, % +Variant, -TableID
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num_tables/1, % -Count
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get_trie_table_link/1, % -Trie
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put_new_trie_table_link/0
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]).
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:- use_module(library(atts)).
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:- use_module(library(lists)).
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:- use_module(library(iso_ext)).
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:- use_module(library(terms)).
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:- use_module(trie).
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:- attribute trie_table_link/1.
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% This file defines a call pattern trie.
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%
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% This data structure keeps the relation between a variant and the
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% corresponding table identifier using a trie. The trick is to make a
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% canonical representation of a given variant using the numbervars/3
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% predicate. The trie uses this canonical representation as key, and
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% the table identifier as value.
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% Uses the (private) global variable trie_table_link
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% This predicate should be called exactly once.
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% It throws an exception if it is called more than once.
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%% table_link_manager_initialize
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%
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% Initializes the global variables `trie_table_link`. Normally
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% called from table_datastructure_initialize/0.
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put_new_trie_table_link :-
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( bb_get(trie_table_link_initialized, _) ->
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true
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; trie_new(Trie),
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put_atts(TrieFlag, trie_table_link(Trie)),
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bb_put(trie_table_link, TrieFlag),
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bb_put(trie_table_link_initialized, [])
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).
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get_trie_table_link(Trie) :-
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bb_get(trie_table_link, TrieFlag),
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get_atts(TrieFlag, trie_table_link(Trie)).
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% PRIVATE
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% mode: + -
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% Variant is not modified
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variant_canonical_representation(Variant, CanonicalRepresentation) :-
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copy_term(Variant, CanonicalRepresentation),
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numbervars(CanonicalRepresentation, 0 ,_).
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% Succeeds if there is a table TableIdentifier in existance for the
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% given call variant Variant.
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p_existing_table(Variant, TableIdentifier) :-
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get_trie_table_link(Trie),
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variant_canonical_representation(Variant, CanonicalRepresentation),
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trie_lookup(Trie, CanonicalRepresentation, TableIdentifier).
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% Important remark: we cannot use an out-of-the-box association list,
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% because we need a lookup based on variant checking, which is not
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% available for such lists. Converting the association list to a
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% regular list => why would you use an association list in the first
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% place...
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p_link_variant_identifier(Variant, TableIdentifier) :-
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get_trie_table_link(Trie),
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variant_canonical_representation(Variant, CanonicalRepresentation),
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trie_insert_succeed(Trie, CanonicalRepresentation, TableIdentifier),
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put_atts(TrieFlag, trie_table_link(Trie)),
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bb_put(trie_table_link, TrieFlag).
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% Returns a list of existing table identifiers.
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% Rather costly.
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get_existing_tables(Ts) :-
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get_trie_table_link(Trie),
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findall(T, trie_get_all_values(Trie, T), Ts).
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% A very unefficient way of implementing this predicate. But it is
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% only used for unit testing, so it doesn't really matter. Also, it
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% doesn't require any additional bookkeeping during the actual
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% execution.
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num_tables(N) :-
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get_existing_tables(Ts),
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length(Ts, N).
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