34 lines
953 B
C++
34 lines
953 B
C++
// Convert text to number and yield expected with number or error text.
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#include "nonstd/expected.hpp"
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#include <cstdlib>
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#include <iostream>
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#include <string>
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using namespace nonstd;
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using namespace std::literals;
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auto to_int( char const * const text ) -> expected<int, std::string>
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{
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char * pos = nullptr;
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auto value = strtol( text, &pos, 0 );
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if ( pos != text ) return value;
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else return make_unexpected( "'"s + text + "' isn't a number" );
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}
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int main( int argc, char * argv[] )
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{
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auto text = argc > 1 ? argv[1] : "42";
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auto ei = to_int( text );
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if ( ei ) std::cout << "'" << text << "' is " << *ei << ", ";
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else std::cout << "Error: " << ei.error();
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}
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// cl -EHsc -wd4814 -I../include 01-basic.cpp && 01-basic.exe 123 && 01-basic.exe abc
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// g++ -std=c++14 -Wall -I../include -o 01-basic.exe 01-basic.cpp && 01-basic.exe 123 && 01-basic.exe abc
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// '123' is 123, Error: 'abc' isn't a number
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