Ichthyostega
b6a39fa831
Now able to remove most complicated comparison operators and most usages of boost::operators... In most cases it is sufficient just to define one ''spaceship operator'', and often even that one can be synthesised. However — we still use boost::operators for arithmetic types, notably the `lib::time::TimeValue`, which is addable and mutipliable
114 lines
3.4 KiB
C++
114 lines
3.4 KiB
C++
/*
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QUERY-TEXT.hpp - syntactical standard representation for queries
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Copyright (C)
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2012, Hermann Vosseler <Ichthyostega@web.de>
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**Lumiera** is free software; you can redistribute it and/or modify it
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under the terms of the GNU General Public License as published by the
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Free Software Foundation; either version 2 of the License, or (at your
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option) any later version. See the file COPYING for further details.
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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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auto operator<=> (QueryText const&) const =default;
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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 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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