Why is size_t unsigned?

[bearophile]

Andrej Mitrovic:

> Actually it used to be a bug that writing to the index 
> /without/ ref
> would end up changing the iteration order, but this was fixed in
> 2.063. It's in the changelog:
>
> http://dlang.org/changelog.html#foreachref

The right design in my opinion is to have the iteration variable 
immutable on default, and mutable/reference on request. This 
saves from bugs and offers new optimization opportunities. But 
unfortunately D doesn't have a "mutable" keyword, D variables are 
generally mutable on default, and Walter seemed not interested in 
my numerous explanations that the mutable foreach iteration 
variable is bug-prone. So Hara has adopted a compromise, now if 
you don't use "ref" the actual iteration variable on an interval 
doesn't change. But it's mutable on default.

So the standard idiom to use foreach on interval needs to be:

foreach (immutable i; 0 .. 10) { ... }

And the programmer has to remove that immutable only where really 
the iteration variable must change :-)

Bye,
bearophile