Ichthyostega
94cec423d0
...which uncovers further deeply nested problems, especially when referring to non-copyable types. Thus need to construct a common type that can be used both to refer to the source elements and the expanded elements, and use this common type as result type and also attempt to produce better diagnostic messages on type mismatch....
142 lines
4.6 KiB
C++
142 lines
4.6 KiB
C++
/*
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BuilderQualifierSupport(Test) - demonstrate accepting arbitrary qualifier terms on a builder function
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Copyright (C) Lumiera.org
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2022, 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 builder-qualifier-support-test.cpp
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** unit test \ref lib::test::BuilderQualifierSupport_test
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*/
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#include "lib/test/run.hpp"
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#include "lib/builder-qualifier-support.hpp"
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#include "lib/test/test-helper.hpp"
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#include <string>
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namespace lib {
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namespace test{
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using std::string;
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namespace { // example strategy to use the builder-qualifier-support...
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/** Example "strategy" class, which can be configured
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* with additional qualifiers at construction */
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class ExampleStrategy
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: BuilderQualifierSupport<ExampleStrategy>
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{
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friend Qualifier one();
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friend Qualifier two(string);
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public:
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ExampleStrategy() = default;
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template<class... QS>
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ExampleStrategy(Qualifier qual, QS... qs)
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: ExampleStrategy{}
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{
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qualify(*this, qual, qs...);
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}
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operator string () const
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{
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return "Strategy{"+prop_+"}";
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}
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private:
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/** a private property
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* to be manipulated by the qualifiers */
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string prop_{"∅"};
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};
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/** definition of a qualifier `one()` */
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ExampleStrategy::Qualifier
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one()
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{
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return ExampleStrategy::Qualifier{[](ExampleStrategy& strategy)
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{
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strategy.prop_ = "!one!";
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}};
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}
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/** definition of another qualifier `two(arg)`, accepting an additional argument */
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ExampleStrategy::Qualifier
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two(string additionalArg)
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{
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return ExampleStrategy::Qualifier{[=](ExampleStrategy& strategy)
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{
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strategy.prop_ += ".two("+additionalArg+")";
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}};
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}
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}//(End)Test example
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/***********************************************************************************//**
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* @test Demonstrate a technique to supply additional descriptive ctor arguments in a type safe way.
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* - target and receiver may be some configurable Strategy etc.
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* - the idea is to provide friend functors, which might tweak or reset internal settings;
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* - these functors are packaged into free standing friend functions with intuitive naming...
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* - which, on call-site, look like algebraic expressions/data-types.
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* @remark because the actual helper function is a free function, it may be integrated
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* in various ways, but typically the support template will be mixed-in, as demonstrated
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* here; this mechanism can be integrated into a constructor call, thus optionally allowing
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* for arbitrary extra qualifiers, even with extra arguments.
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*
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* @see builder-qualifier-support.hpp
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*/
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class BuilderQualifierSupport_test : public Test
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{
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void
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run (Arg)
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{
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ExampleStrategy f0;
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CHECK (f0 == "Strategy{∅}"_expect);
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ExampleStrategy f1(one());
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CHECK (f1 == "Strategy{!one!}"_expect);
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ExampleStrategy f2(two("Ψ"));
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CHECK (f2 == "Strategy{∅.two(Ψ)}"_expect);
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ExampleStrategy f3(one(), two("↯"));
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CHECK (f3 == "Strategy{!one!.two(↯)}"_expect);
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ExampleStrategy f4(two("☭"), one());
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CHECK (f4 == "Strategy{!one!}"_expect); // Note: evaluated from left to right, one() overwrites prop_
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}
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};
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/** Register this test class... */
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LAUNCHER (BuilderQualifierSupport_test, "unit common");
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}} // namespace lib::test
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