This short C++ program behaves in a way which baffles me:
#include <cassert>
#include <iostream>
#include <string>
#include <boost/lexical_cast.hpp>
int main(void) {
signed char c = -2;
assert(c == -2);
c = boost::lexical_cast<signed char>(std::string("-2"));
std::cout << c << "\n";
}
Using g++ 5.2.1
and boost-1.58.0
, I get:
terminate called after throwing an instance of 'boost::exception_detail::clone_impl >' what(): bad lexical cast: source type value could not be interpreted as target
Why can't Boost cast from string "-2" to signed char
given that the value -2
is representable by this type?
The solution is to use Boost:
#include <boost/lexical_cast.hpp>
#include <boost/numeric/conversion/cast.hpp>
int tmp = boost::lexical_cast<int>(std::string("-2"));
char c = boost::numeric_cast<signed char>(tmp);
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