29 lines
746 B
C++
29 lines
746 B
C++
#include "nonstd/optional.hpp"
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#include <cstdlib>
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#include <iostream>
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using nonstd::optional;
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using nonstd::nullopt;
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optional<int> to_int( char const * const text )
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{
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char * pos = NULL;
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const int value = static_cast<int>( strtol( text, &pos, 0 ) );
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return pos == text ? nullopt : optional<int>( value );
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}
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int main( int argc, char * argv[] )
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{
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const char * text = argc > 1 ? argv[1] : "42";
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optional<int> oi = to_int( text );
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if ( oi ) std::cout << "'" << text << "' is " << *oi << std::endl;
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else std::cout << "'" << text << "' isn't a number" << std::endl;
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}
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// cl -nologo -W3 -EHsc -I../include to_int.cpp && to_int x1
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// g++ -Wall -Wextra -std=c++03 -I../include -o to_int.exe to_int.cpp && to_int x1
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