On Tuesday, 25 November 2014 at 15:42:13 UTC, Kagamin wrote:
Correctness is an emergent property - when behavior matches expectation, so overflow has variable correctness in various parts of the code.
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.
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.
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.
