Convert a string to a unsigned long long in c++

Question

Convert a string to a unsigned long long.

string str = "0x1232"

How do I convert to a unsigned long long.

This is what i've tried.

unsigned long long ull;
ull = stoull(str, NULL, 0);

Error:

 error: identifier "stoull" is undefined
                        ull = stoull(str, NULL, 0);

Can you give me some pointers?

score 8 · Accepted Answer · answered Jan 29 '14 at 05:24

8

First of all it's strtoull (notice the r). Second of all, it's an old C-style function and can't handle std::string directly. You either have to pass it str.c_str() or use the new std::stoull.

answered Jan 29 '14 at 05:24

Some programmer dude

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Could you give an example? – pistal Jan 29 '14 at 05:25
@pistal, Here's one for `std::stoi`, which is really close to `std::stoull`: http://en.cppreference.com/w/cpp/string/basic_string/stol – chris Jan 29 '14 at 05:27
I get the following error: error: namespace "std" has no member "stoull" ull = std::stoull(str,NULL,16); – pistal Jan 29 '14 at 05:32
@pistal Then your compiler is to old and don't have the C++11 `std::stoull`. You have to use `strtoull`, but change the argument accordingly. – Some programmer dude Jan 29 '14 at 05:33
Thank you. I tried the following: error: no instance of function "strtoull" matches the argument list argument types are: (std::string, long, int) ull = strtoull(str,NULL,10); http://stackoverflow.com/a/1646085/2015933 – pistal Jan 29 '14 at 05:36
@pistal Please read my answer again, it contains the solution to that too. – Some programmer dude Jan 29 '14 at 05:41
I have used strtoull.. and not stoull. I don't see the problem. – pistal Jan 29 '14 at 06:01
@pistal The problem is that `strtoull` is an old C-style function, that takes a `const char*` argument and not `std::string`. – Some programmer dude Jan 29 '14 at 06:05
So, Should I use str.c_str() instead? Could you point me to an examle or give me one? – pistal Jan 29 '14 at 06:08
2

@pistal Yes that's correct. Just e.g. `ull = std::strtoull(str.c_str(), 0, 16);` – Some programmer dude Jan 29 '14 at 06:12

Convert a string to a unsigned long long in c++

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