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What's the C++ way of parsing a string (given as char *) into an int? Robust and clear error handling is a plus (instead of returning zero).
What's the C++ way of parsing a string (given as char *) into an int? Robust and clear error handling is a plus (instead of returning zero).
In the new C++11 there are functions for that: stoi, stol, stoll, stoul and so on.
int myNr = std::stoi(myString);
It will throw an exception on conversion error.
Even these new functions still have the same issue as noted by Dan: they will happily convert the string "11x" to integer "11".
See more: http://en.cppreference.com/w/cpp/string/basic_string/stol
I think these three links sum it up:
stringstream and lexical_cast solutions are about the same as lexical cast is using stringstream.
Some specializations of lexical cast use different approach see http://www.boost.org/doc/libs/release/boost/lexical_cast.hpp for details. Integers and floats are now specialized for integer to string conversion.
One can specialize lexical_cast for his/her own needs and make it fast. This would be the ultimate solution satisfying all parties, clean and simple.
Articles already mentioned show comparison between different methods of converting integers <-> strings. Following approaches make sense: old c-way, spirit.karma, fastformat, simple naive loop.
Lexical_cast is ok in some cases e.g. for int to string conversion.
Converting string to int using lexical cast is not a good idea as it is 10-40 times slower than atoi depending on the platform/compiler used.
Boost.Spirit.Karma seems to be the fastest library for converting integer to string.
ex.: generate(ptr_char, int_, integer_number);
and basic simple loop from the article mentioned above is a fastest way to convert string to int, obviously not the safest one, strtol() seems like a safer solution
int naive_char_2_int(const char *p) {
int x = 0;
bool neg = false;
if (*p == '-') {