I'm having trouble here with this code:
unsigned long value = stoul ( s, NULL, 11 );
that gives me this error with c++ 98
error: 'stoul' was not declared in this scope
It works on C++11, but I need this on C++98.
You can use strtoul
from cstdlib
:
unsigned long value = strtoul (s.c_str(), NULL, 11);
Some differences:
std::stoul
is a size_t *
which will be set to the position of the first character after the converted number, while the second argument of strtoul
is of type char **
and points to the first character after the converted number.std::stoul
throw a invalid_argument
exception while strtoul
does not (you must check the value of the second argument). Typically, if you want to check for error:char *ptr;
unsigned long value = strtoul (s.c_str(), &ptr, 11);
if (s.c_str() == ptr) {
// error
}
unsigned long
, std::stoul
throws a out_of_range
exception while strtoul
return ULONG_MAX
and set errno
to ERANGE
.Here is custom version of std::stoul
that should behave like the standard one and summarizes the difference between std::stoul
and strtoul
:
#include <string>
#include <stdexcept>
#include <cstdlib>
#include <climits>
#include <cerrno>
unsigned long my_stoul (std::string const& str, size_t *idx = 0, int base = 10) {
char *endp;
unsigned long value = strtoul(str.c_str(), &endp, base);
if (endp == str.c_str()) {
throw std::invalid_argument("my_stoul");
}
if (value == ULONG_MAX && errno == ERANGE) {
throw std::out_of_range("my_stoul");
}
if (idx) {
*idx = endp - str.c_str();
}
return value;
}
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