Implementing Half Floats in D

[H. S. Teoh]

On Tue, Jan 29, 2013 at 01:44:20AM +0100, bearophile wrote:
> Walter Bright:
> 
> >http://www.drdobbs.com/cpp/implementing-half-floats-in-d/240146674
> 
> From the article:
> 
> >Built-in types tend to run faster because the optimizer can take
> >advantage of mathematical identities,<
> 
> Generally in D we like the compiler to verify user-applied
> annotations like pure and const. For the compiler of a normal
> language today it's probably too much difficult to prove the
> theorems coming from those identities on user defined types. But if
> the compiler assumes the programmer to be right on this (because
> such types are usually defined in well reviewed libraries), then I
> think it's not too much hard to invent a small set of @annotations
> that attached to a user defined struct tell the compiler to allow
> some optimizations typical of integral numbers, floating point
> numbers, complex numbers, gaussian integers, quaternions, octonions
> and few others, according to them having associative, commutative,
> etc, properties, or not having them.
[...]

+1.  I've always wanted a language capable of user-specified
optimizations for custom types. This would be very useful on things like
matrix types, which would otherwise require heavy trickery with
expression templates in order to produce efficient code.


T

-- 
May you live all the days of your life. -- Jonathan Swift