135 lines
4 KiB
C++
135 lines
4 KiB
C++
/*
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QUERY-TEXT.hpp - syntactical standard representation for queries
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Copyright (C) Lumiera.org
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2012, Hermann Vosseler <Ichthyostega@web.de>
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License as
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published by the Free Software Foundation; either version 2 of
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the License, or (at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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/** @file query-text.hpp
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** A generic syntactical representation for all kinds of queries.
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** Within Lumiera, its a common pattern to query for parts to be combined,
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** instead of using a hard wired builder logic. Consequently, there are various
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** flavours of queries used by different subsystems. As a common denominator,
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** we use a syntactical query representation, based on predicate notation
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** (mathematical logic, using prolog syntax). While subsystems typically
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** might resolve a specialised query directly, as a fallback this
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** syntactical representation allows for \em generic query dispatch.
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** And it can be used as intermediary format for remolding queries.
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**
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** @note as of 12/2012 this AST-representation is not defined at all;
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** instead we use a plain string as placeholder for the "real thing"
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** @todo actually build the term representation /////////////////////////////TICKET #899
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**
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** @see QueryText_test usage example
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**
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*/
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#ifndef LIB_QUERY_TEXT_H
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#define LIB_QUERY_TEXT_H
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#include "lib/error.hpp"
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#include "lib/hash-value.h"
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#include "lib/query-util.hpp"
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#include "lib/util.hpp"
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#include <string>
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namespace lib {
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using lib::HashVal;
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using std::string;
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/**
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* Syntactical query representation.
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* Used as a backbone to allow for generic queries and to
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* enable programmatically rebuilding and remolding of queries.
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*
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* @todo this is placeholder code and just embeds a string
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* with the raw query definition, instead of parsing
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* the definition and transforming it into an AST
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*
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* @see Query
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*/
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class QueryText
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{
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string definition_;
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public:
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QueryText() { }
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QueryText (string const& syntacticRepr)
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: definition_ (normalise (syntacticRepr))
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{ }
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// using default copy/assignment
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operator string() const
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{
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return definition_;
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}
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bool
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empty() const
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{
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return definition_.empty();
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}
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bool
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hasAtom (string const& predSymbol)
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{
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return util::contains (definition_, predSymbol);
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}
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/** synthetic total order to classify query definitions.
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* Queries with more specific conditions should yield larger values.
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* @warning this is rather a design idea and it's not clear
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* if this metric can be made to work in practice
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* @todo using a rather deaf placeholder implementation
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* based just on counting the top level predicates.
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*/
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uint
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degree_of_constriction() const
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{
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return query::countPred (definition_);
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}
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private:
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string normalise (string const& rawDefinition);
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friend bool
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operator== (QueryText const& q1, QueryText const& q2)
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{
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return q1.definition_ == q2.definition_;
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}
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friend bool
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operator< (QueryText const& q1, QueryText const& q2)
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{
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return q1.definition_ < q2.definition_;
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}
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friend HashVal hash_value (QueryText const& entry);
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};
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} // namespace lib
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#endif /*LIB_QUERY_TEXT_H*/
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