what is 1UI64 type?

Question

I recently saw this 1UI64 type. I didnt get what kind of type is it. How can they use 1 before ?

which compiler provides this extension? – Jens Gustedt Nov 22 '10 at 19:07 — Jens Gustedt, Nov 22 '10 at 19:07

score 8 · Accepted Answer · answered Nov 22 '10 at 18:16

8

It's not a type, it's a 64-bit constant integer of value 1.

answered Nov 22 '10 at 18:16

RichieHindle

score 5 · Answer 2 · edited May 23 '17 at 12:21

5

In Microsoft C/C++ The I64 part of the expression is a suffix for integer constants that indicates the constant should be a 64-bit type:

This is a Microsoft extension, even though the docs don't call that out.

A somewhat more portable way to specify such a constant might be to include <stdint.h> and use UINT64_C(1) - MSVC has stdint.h as of VS2010.

For versions prior to that you might consider the options provided in this SO question: C99 stdint.h header and MS Visual Studio

edited May 23 '17 at 12:21

Community

answered Nov 22 '10 at 20:12

Michael Burr

1

you could also mention the C99 version `UINT64_C(1)` from `stdint.h` – Christoph Nov 23 '10 at 10:46
@Christoph: Done. I had a mention about `UINT64_C()` in my answer at first, but decided to leave it out since MSVC complicates the `stdint.h` situation a little. But since you suggested it, I added it back with a bit of detail. – Michael Burr Nov 24 '10 at 03:11

score 4 · Answer 3 · answered Nov 22 '10 at 18:15

4

That's an unsigned 64-bit 1.

answered Nov 22 '10 at 18:15

thelost

score 2 · Answer 4 · answered Nov 22 '10 at 18:14

2

Probably nonstandard Unsigned Integer 64-bit, or a fixed point 0.64 format.

answered Nov 22 '10 at 18:14

ysap

4 Answers4