I've been looking at code for the find()
function for strings, and they store the result of that in a variable with data type size_t. However it is my understanding that size_t is an unsigned int, and if find()
does not find the intended string, it returns -1. For example if I have
string s = "asdf";
size_t i = s.find("g")
cout << i;
It gives me 4294967295. However if I replace size_t with the int data type, it gives me -1. The strange thing is when I make a comparison like
string s = "asdf";
size_t i = s.find("g")
if (i == -1) { do_something; }
it works whether i is size_t or int. So which do I use? int or size_t?
Neither.
Under the std::string::find
documentation , it recommends that you use string::size_type
and string::npos
to detect not found in find
:
std::string::size_type i = s.find("g");
if (i == std::string::npos) std::cout << "Not Found\n";
It shouldn't be surprising that int
and size_t
can be compared with -1 and work, they will have the bits, so when cast to do the comparison they will compare equally, you should however receive a warning such as:
warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
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