'int' is enough for 'length' to migrate code from x86 to x64

[Kagamin via Digitalmars-d]

On Tuesday, 25 November 2014 at 15:52:22 UTC, Ola Fosheim Grøstad 
wrote:
> I assume you are basically saying that Walter's view that 
> matching C++ is more important than getting it right, because 
> some people might expect C++ behaviour. Yet Ada chose a 
> different path and is considered a better language with respect 
> to correctness.

C++ legacy is huge especially in culture. That said, the true 
issue is in beliefs (which probably stem from 16-bit era). Can't 
judge Ada, have no experience with it, though examples of Java 
and .net show how marginal is importance of unsigned types.

> I think it is important to get the definitions consistent and 
> sound so they are easy to reason about, both for users and 
> implementors. So one should choose whether the type is 
> primarily monotonic, with incorrect values "truncated into" 
> modulo N, or if the type is primarily modular.

In this light examples by Marco Leise become interesting, he 
tries to evade wrapping even for unsigned types, so, yes types 
are primarily monotonic and optimized for small values.

> If addition is defined to be primarily monotonic it means you 
> can optimize "if(x < x+1)…" into "if (true)…". If it is defined 
> to be primarily modular, then you cannot.

Such optimizations have a bad reputation. If they were more 
conservative and didn't propagate back in code flow, the 
situation would be probably better. Also isn't (x < x+1) a 
suspicious expression, is it a good idea to mess with it?