cent/ucent

[bearophile]

This is one of the last dmd changes:
http://www.dsource.org/projects/dmd/changeset/557

cent/ucent are probably easy to implement, their implementation can require little code on 64 bit systems, and operations done among them are probably fast on 64 bit systems.

128 bit unsigned numbers can represent:
340_282_366_920_938_463_463_374_607_431_768_211_455
Many normal programs don't overflow such numbers. A cent number can also be used to store safely the result of many operations done on 64 bit values. And generally I like the idea of having them...

But while I know of few scientific computations situations where quadruple precision floating point numbers can be useful, in practice I don't know of situations where cent/ucent can be useful.

One possible situation where ucent can be useful is to perform bitwise operations on 128-bits-wide SSE registers. But a good D compiler can use exactly the same CPU instructions when those operators are used among uint[4] fixed-sized arrays.

So unless some significant application can be found, I suggest to not add cent/ucent. All features in the language need a purpose, adding useless things is bad. They can be kept among reserved keywords (as 'macro') for possible 128-bit CPUs.

On the other hand instead of cent/ucent I have several situations (not related with cryptography) where I'd like in D a built-in "bint" or "bigint", that is the multi-precision integers (currently in a std.bigint module... well, the module was present in 2.046, I can't see it in Phobos of 2.047, I don't know why). Having it built-in allows for better multi-precision literals.

(There are other number types that probably are more useful than cent/ucent, like a decimal floating point (IEEE standard 854-1987), useful for concurrency.)

Bye,
bearophile