On Wednesday, 21 August 2013 at 16:21:47 UTC, Ramon wrote:
As for generics, let me put it this way:
In Eiffel generics have been an integral part of the language
design from the beginning. In D ways and mechanisms are
provided to achieve what quite usually is the goal of generics,
namely generic algorithms in way, i.e. by having to write code
for an algorithm just once. That might seem to be a minor
difference, in particular when looking from a "Huh? I can get
it done, so what's the fuss all about, eh?" perspective.
Of course, there the C and successors worlds proponents are
right, this incurs a price (which templates do, too ...) and,
yes, in the end, somewhere someone or something must sort the
types out anyway (because of the way CPUs work).
There are basically two ways to implement generics. Type erasure
(Java,Haskell) or template instantiation (C++,D). Instantiation
provides better performance, but sacrifices error messages
(fixable?), binary code size, and compilation modularity
(template implementation must be available for instantiation).
Type safety is not a problem in either approach.
Longer form: http://beza1e1.tuxen.de/articles/generics.html
An interesting twist would be to use type erasure for reference
types and instantiation for value types. Another idea could be to
use instantiation selectively as an optimization and erasure in
general.
Another example is data types, concretely integers. Ada offers
a nice way do precisely nail down precision/storage. If I want
to store days_of_month I can have an integer type holding ints
between 1 and 31 (which, due to the way they implemented it can
be a PITA). Eiffel gives me something quite similar (in a more
elegant way) and additionally a "dumb" INTEGER (32 or 64 bit)
and than a gazillion subtypes like "INTEGER_16". That's great
because in a quick and dirty script a plain integer (max size
of CPU) is good enough and keeps life simple. If I need
days_of_month I can very easily have that as int type.
In D you can use structs:
struct days_of_month {
int day;
/* fill in operator overloading etc */
}
