Convert -1 to uint C#

Question

Converting -1 to uint will not work "((uint)(-1))" solution?

num10 = ((uint)(-1)) >> (0x20 - num9);

Error: Constant value '-1' cannot be converted to a 'uint' (use 'unchecked' syntax to override)

-1 is outside the range of an unsigned integer. – Austin Brunkhorst Mar 17 '13 at 06:03 — Austin Brunkhorst, Mar 17 '13 at 06:03
Does the error message not tell you the solution? – ta.speot.is Mar 17 '13 at 06:06 — ta.speot.is, Mar 17 '13 at 06:06

score 12 · Answer 1 · answered Mar 17 '13 at 06:04

12

Use

uint minus1 = unchecked((uint)-1);
uint num10 = (minus1) >> (0x20 - num9);

Or even better

uint num10 = (uint.MaxValue) >> (0x20u - num9);

answered Mar 17 '13 at 06:04

p.s.w.g

score 2 · Answer 2 · answered Mar 17 '13 at 06:03

2

The compiler is telling you what you need to do:

unchecked
{
     num10 = ((uint)(-1)) >> (0x20 - num9);
}

However, it may not give you the result you want.

answered Mar 17 '13 at 06:03

Inisheer

score 1 · Answer 3 · answered Mar 17 '13 at 06:03

1

An unsigned integer can represent positive values only. It can't represent -1.

If you want to represent negative values, you'll need to use a signed type, like int.

answered Mar 17 '13 at 06:03

Michael Petrotta

score 1 · Answer 4 · answered Mar 17 '13 at 06:04

1

Look up the unchecked context.

answered Mar 17 '13 at 06:04

UncleO

score 1 · Answer 5 · answered Jul 31 '14 at 14:16

You can indeed have something that resembles negative, unsigned numbers somewhat. They have the feature that x + (-x) == 0

To create a "negative" uint in c# without unchecked regions, you can instead use the equivalent (~x) + 1 which is the same as -x

5 Answers5