In limits.h, there are #defines for INT_MAX and INT_MIN (and SHRT_* and LONG_* and so on), but only UINT_MAX.
Should I define UINT_MIN myself? Is 0 (positive zero) a portable value?
views:
178answers:
3
+17
A:
It's an unsigned integer - by definition its smallest possible value is 0. If you want some justification besides just common sense, the standard says:
6.2.6.2 Integer types
- For unsigned integer types other than
unsigned char, the bits of the object representation shall be divided into two groups: value bits and padding bits (there need not be any of the latter). If there are N value bits, each bit shall represent a different power of 2 between 1 and 2^(N−1), so that objects of that type shall be capable of representing values from 0 to 2^(N−1) using a pure binary representation; this shall be known as the value representation. The values of any padding bits are unspecified.
Carl Norum
2010-08-17 04:25:56
love the standard. especially when it's quoted.
Matt Joiner
2010-08-17 04:51:30
This does not answer my question.
Ariel Bold
2010-08-18 04:23:23
@Ariel, how does it not answer your question? The minimum value for an unsigned type is defined by the standard to be 0.
Carl Norum
2010-08-18 06:29:02
+6
A:
You could use std::numeric_limits<unsigned int>::min().
Kirill V. Lyadvinsky
2010-08-17 04:56:32
This will work in C++, and this will not work in C. What is C/C++?
Kirill V. Lyadvinsky
2010-08-18 04:57:14
Our source tree contains C and C++ and so this need to work with both. This is why I tagged the question with both.
Ariel Bold
2010-08-18 05:24:01
+1
A:
If you want to be "typesafe" you could use 0U, so if you use it in an expression you will have the correct promotions to unsigned.
Jens Gustedt
2010-08-17 09:33:55
Thinking of it, it is perhaps not so a good idea to have a file that has the same name as a standard file or to mess around with the later. I'd put it another place. If you want to have a `+` to the `0U` (why?) you should have the whole in parenthesis `(+0U)` since otherwise you might have unwanted effects when the `+` could be interpreted as addition.
Jens Gustedt
2010-08-18 06:53:20
You don't need parenthesis. Even in `1+UINT_MIN`, it would expand to `1+ +0U`, which is a correct expression. Macro expansion happens at token level, and will not glue the two plusses together.
MSalters
2010-08-18 10:47:48
@MSalters: I think you need it since it makes invalid sequences valid. Something like `5 UINT_MIN` would become valid, where it really shouldn't.
Jens Gustedt
2010-08-18 11:26:51
@Jens: Using that logic, I can equally say that you must _not_ have parenthesis as it makes invalid sequences valid. Something like `sin UINT_MIN` becomes valid.
MSalters
2010-08-18 14:46:17
@MSalters: good point. So it is a matter of taste which invalid sequences should become valid ;-) Brings us back to the question, why using the `+` in the first place? `0U` would be much simpler, then, and is really a well defined constant.
Jens Gustedt
2010-08-18 15:26:16