On 2011-01-31 12:55:07 +0100, Simen kjaeraas said:
ElementType!Range minArg( alias fun, Range )( Range range, out
ReturnType!fun ) {
...
}
Aaaah. I guess I tried ElementType(Range), forgetting to make it a
compile-time parameter. Thanks. (Hadn't seen ReturnType; makes sense :)
Might I also ask why you use an out parameter instead of a tuple return?
Well... I had a tuple return at first, but one of the advantages of
returning multiple values that I'm accustomed to is the ability to
assign to multiple variables, such as
arg, val = minArg(...)
(Yeah, I'm a Python guy... ;)
As far as I can see, you can't do that here? Using result[0] and
result[1] or the like, or assigning separately to two variables just
seemed more cumbersome. Then again, I could use a tuple with named
members, I guess. In your opinion, what would be the prettiest (in D
terms) way of doing this?
[snip]
D currently does not support template currying to any good degree.
OK. Well, I guess I don't really need it. Still trying to get a feel
for what's "normal" D :)
However, there is at least one library out there that does that for you:
http://www.dsource.org/projects/dranges
In the file templates.d, there is the template CurryTemplate, which
rewrites a template to a set of nested templates. This would allow you
to partially instantiate a template, and add more parameters as you go.
I see. I actually don't mind writing nested templates myself -- but for
some reason I couldn't get them to work properly. (D kept complaining
about declarations vs instances, and the like; I guess I'll have a look
at how dranges does it.)
I've been able to make either one of these two pieces of functionality
work with some twiddling and nesting (i.e., *either* instantiating
optArg into minArg/maxArg, *or* instantiating explicitly defined
minArg/maxArg into specialized functions) but combining them has so far
eluded me (unless I start fiddling with strinc constants and mixin(),
which seems excessively hacky for such a simple thing).
dranges' templates.CurryTemplate should take care of some of your problems.
Not sure if it will fix them all.
OK, thanks.
By the way, if you have suggestions for other more "D-like" ways of
encapsulating this functionality (basically a linear scan for an
element that yields a max/min value for a given expression), I'd be
interested to hear that too. The best way to solve a problem is often
to rephrase it :)
--
Magnus Lie Hetland
http://hetland.org
