Annoyance with new integer promotion deprecations

[Dmitry Olshansky]

On Monday, 5 February 2018 at 20:45:22 UTC, H. S. Teoh wrote:
> On Mon, Feb 05, 2018 at 03:23:20PM -0500, Steven Schveighoffer 
> via Digitalmars-d wrote:
>> On 2/5/18 2:30 PM, H. S. Teoh wrote:
>> > Even better yet:
>> > 
>> > 	byte b;
>> > 	b = -b;		// Deprecation error
>> > 
>> > WAT????
>> 
>> In the future, -b will be typed as an int, so you can't 
>> reassign it to b.  You can see this today with 
>> -transition=intpomote:
>> 
>> Error: cannot implicitly convert expression -cast(int)b of 
>> type int to
>> byte
> [...]
>
> Honestly, this just makes narrow int types basically useless 
> when it comes to any arithmetic at all.
>

In fact you really shouldn’t do arithmetic on narrow integers, 
especially as loop counters.
It usually results in suboptimal machine code on optimizing 
compilers.

That leaves arrays of bytes and array-wise operations though, 
SIMD by definition can operate on a pack of e.g. byte-sized 
integers.

Bottom line is to use narrow integers only as a way to pack data 
and for SIMD operations in arrays.

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> T