On 07/12/13 12:08, Jordi Boggiano wrote:
On Sat, Dec 7, 2013 at 2:01 AM, spir <denis.s...@gmail.com> wrote:
On 12/07/2013 01:12 AM, Gaetan wrote:
I am in favor of two version of the api: from_str which has already done
the unwrap, and a from_str_safe for instance that returns a Result or
option.
This provides the important semantic information (that I've evoked at the
end end of a long earlier reply in this thread) of whether func failure is
expected and belongs to the logic of the present app and we must deal with
it, or not.
But I'm still shared on this topic for finding it also annoying, like Simon,
to have to duplicate whole catogories of such funcs (of which we cannot know
in advance whther they'll fail or not), if only the interface as apparently
proposed by Gaëtan.
Syntax sugar like this would be nice:
let str = std::str::from_utf8("Parse this optimistically, and fail otherwise");
// str is a string or the task fails
vs.
let opt_str = std::str::from_utf?("Parse this if valid"); // note the
question mark
if opt_str.is_some() { .... }
Problem is, this sounds scary to implement at the compiler level, if
it's possible at all :) I am just throwing it out there for others to
judge.
Cheers
I personally think a better solution is something like Haskell's do
notation[1], where you can chain several computations that return
Option<..> such that if any intermediate one returns None, the later
ones are not evaluated and the whole expression returns None, which
saves having to call .get()/.unwrap()/.expect() a lot.
This can work for types like Result too (in fact, the Haskell
implementation of `do` is sugar around some monad functions, so any
monad can be used there; we currently don't have the power to express
the monad typeclass/trait in Rust so the fully general form probably
isn't possible as a syntax extension yet, although a limited version is).
Huon
[1]: http://en.wikibooks.org/wiki/Haskell/do_Notation
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