I'm building a function (or template or whatever, really) that is
related to map and minPos in std.algorithm. Basically, it's the
standard mathematical argmin, except that it also returns min. It looks
something like this:
auto minArg(alias fun, Range, T)(Range range, out T minVal) {
...
}
Already there may be issues -- the return type should be
ElementType(range) and T should be the return type of fun ... but it
works. (Suggestions on these issues are welcome, but that's not really
the main point here.)
The thing is, because I'm also returning the actual value, I'd rather
not use the strategy of std.algorithm.minPos, which asks you to use an
inverted function to get maxPos; instead, I'd like an explicit maxArg
function. My idea was to have a common, more general optArg, which took
an operator ("<" or ">") as a compile-time argument. Then I could do
something like
alias optArg!"<" minArg;
alias optArg!">" maxArg;
Then, at some *later* time, I might want to do something like:
alias maxArg!((v) {return dist(u,v);}) farthest;
(By the way: For some reason, I'm not allowed to use curry(dist,u)
instead of the lambda here, it seems. Any insights on that? Would have
been nice to use "d(u,a)" as well -- as I do use unaryFunc on the fun
argument. That doesn't work either, though...)
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).
Any ideas/suggestions? I'm sure I'm missing something obvious ...
(Perhaps even existing functionality for minArg/maxArg -- although the
general question still stands.)
--
Magnus Lie Hetland
http://hetland.org
