## digitalmars.D - uint is NOT just a positive number

• Kagamin (2/2) Oct 07 2009 Some people used to use unsigned integers as 'mere' non-negative numbers...
• Don (10/12) Oct 07 2009 Amen!
• Jeremie Pelletier (9/31) Oct 07 2009 I think it also depend on the representation of that number, for example...
Kagamin <spam here.lot> writes:
```Some people used to use unsigned integers as 'mere' non-negative numbers, but
they're actually not numbers from range, they're numbers from entirely
different algebra. And - yes - this causes subtle bugs. Recent introduction of
integer range promotions works hard in hiding those bugs, so they manifest only
in very rare corner cases.

Ever wondered wheter a-=b and a+=-b equivalent? In most cases they are, except
for one. Do you remember? uint is not propagated to long. I've hit it recently.
It's exactly because unsigneds are not just non-negative numbers. So it's pain
to see their wide use as numbers for which sign-sensitive arithmetic operations
are meaningful.
```
Oct 07 2009
Don <nospam nospam.com> writes:
```Kagamin wrote:
Some people used to use unsigned integers as 'mere' non-negative numbers, but
they're actually not numbers from range, they're numbers from entirely
different algebra. And - yes - this causes subtle bugs.

Amen!
I actually think it's worse in D, because 'uint' is so easy to type,
it's far more seductive than 'unsigned int'.

Recent introduction of integer range promotions works hard in hiding
those bugs, so they manifest only in very rare corner cases.

It's not complete. It doesn't apply to arithmetic operations yet. Once
that's in place, D could become really harsh about mixing signed and
unsigned: if there's any chance the highest bit is set in the signed
type, mixing signed and unsigned should be illegal.

Ever wondered wheter a-=b and a+=-b equivalent? In most cases they are, except
for one. Do you remember? uint is not propagated to long. I've hit it recently.
It's exactly because unsigneds are not just non-negative numbers. So it's pain
to see their wide use as numbers for which sign-sensitive arithmetic operations
are meaningful.

```
Oct 07 2009
Jeremie Pelletier <jeremiep gmail.com> writes:
```Don wrote:
Kagamin wrote:
Some people used to use unsigned integers as 'mere' non-negative
numbers, but they're actually not numbers from range, they're numbers
from entirely different algebra. And - yes - this causes subtle bugs.

Amen!
I actually think it's worse in D, because 'uint' is so easy to type,
it's far more seductive than 'unsigned int'.

Recent introduction of integer range promotions works hard in hiding
those bugs, so they manifest only in very rare corner cases.

It's not complete. It doesn't apply to arithmetic operations yet. Once
that's in place, D could become really harsh about mixing signed and
unsigned: if there's any chance the highest bit is set in the signed
type, mixing signed and unsigned should be illegal.

Ever wondered wheter a-=b and a+=-b equivalent? In most cases they
are, except for one. Do you remember? uint is not propagated to long.
I've hit it recently. It's exactly because unsigneds are not just
non-negative numbers. So it's pain to see their wide use as numbers
for which sign-sensitive arithmetic operations are meaningful.

I think it also depend on the representation of that number, for example
most numbers I would feel more natural as hex value such bit fields and
flags, address offsets, and whatnot are all unsigned, almost everything
else is signed.

I did get annoyed about uint not automatically propagated to long
however, when I was reading lo/hi uint offset pairs from a file and
making it a long offset (lo + (hi<<32)), turns out it can't be done
without explicit long casts.
```
Oct 07 2009