On 23/04/2013 8:53 AM, Diggory Hardy wrote:
I suspect (please correct me if I'm wrong) that if it wasn't for C and x86
compatibility then most people would fall into two categories: don't
know/don't care, and prefer F-division. It's one of those little things like
tau vs. pi which would have been less confusing if we'd started off on the
other foot to start with.
And IP addresses would have been 64 or 128bit from the start, there
would only be one endianness, and so forth ... yes, sure. But we don't
cast off the weight of the past so easily, and I do not think this is
something it's wise to fiddle with.
A very widely-applied design choice in rust is that the basic types are
machine-sized and the arithmetic operations on them are (as close as
reasonable to) machine operations. The machine operation is remainder.
Moreover, it's not "just C and x86". This same choice is taken (more or
less) by PowerPC, LLVM, C++, C#, Java, D, Go, JS, Scala, Ocaml, etc. etc.
The path we've taken here is to admit _two_ operation-pairs, div/mod and
quot/rem. This path is taken by several languages and specs (Scheme,
Common Lisp, Ruby, Smalltalk, SML, Prolog, Haskell, Ada, and ISO 10967
and IEEE 754). The work for this landed last week:
https://github.com/mozilla/rust/pull/5990
https://github.com/mozilla/rust/pull/6013
https://github.com/mozilla/rust/issues/4565
https://github.com/mozilla/rust/issues/4917
(Phew! This must really be the week for integer division!)
The only remaining thing to struggle with is "which of the two
operation-pairs to assign the / and % symbols to", in the
operator-overloading sense. For this, we've gone with quot/rem, as in
the other languages above, and in keeping with the design preference
above. You have to call .mod() or .div() to get the other operators.
It does mean there's a bit of a footgun surrounding the symbols / and %
specifically, on signed integer types. I would not be at all opposed to
adding a lint flag to calls-to-/-and-%-on-signed-integer-types, such
that you could trap them all. As with many things here, the design space
includes a variety of (sensible) preferences.
-Graydon
(Please correct me if I've swapped which of the two meanings we've
actually assigned; this is one of those issues like double-negation and
off-by-one indexing where I get things backwards no matter how much
energy I spend on making sure I get it right.)
_______________________________________________
Rust-dev mailing list
[email protected]
https://mail.mozilla.org/listinfo/rust-dev
