afb81b8278
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69 lines
1.4 KiB
C++
69 lines
1.4 KiB
C++
// Use a non-ignorable value with expected.
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#include "nonstd/expected.hpp"
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#include <iostream>
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using namespace nonstd;
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template< typename T >
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class required
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{
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public:
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required( T const & value)
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: content( value ) {}
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required( required && other )
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: content( other.content )
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, ignored( other.ignored )
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{
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other.ignored = false;
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}
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required( required const & other ) = delete;
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~required() noexcept( false )
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{
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if ( ignored )
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throw std::runtime_error("required: content unobserved");
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};
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T const & operator *() const { ignored = false; return content; }
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private:
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T content;
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mutable bool ignored = true;
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};
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template< typename T >
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auto make_required( T value ) -> required<T>
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{
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return required<T>( std::move(value) );
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}
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using unused_type = char;
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auto produce( int value ) -> expected< required<int>, unused_type >
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{
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return make_required( std::move(value) );
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}
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int main( int argc, char * argv[] )
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{
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try
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{
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auto er42 = produce( 42 );
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auto er13 = produce( 13 );
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std::cout << "value: " << **er42 << "\n";
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}
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catch ( std::exception const & e )
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{
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std::cout << "Error: " << e.what();
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}
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}
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// cl -EHsc -wd4814 -Zc:implicitNoexcept- -I../include 02-required.cpp && 02-required.exe
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// g++ -std=c++14 -Wall -I../include -o 02-required.exe 02-required.cpp && 02-required.exe
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// value: 42
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// Error: required: content unobserved
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