sortOn: sorts range of aggregates by member name(s)

["Nordlöw" via Digitalmars-d]

On Wednesday, 5 November 2014 at 21:29:20 UTC, Marc Schütz wrote:
> Again untested:
>
> private alias makePredicate(alias xtr) =
>     (a, b) => (extractorFun!xtr(a) < extractorFun!xtr(b));

This errors as

sort_ex.d(35,43): Error: basic type expected, not (
sort_ex.d(35,43): Error: function declaration without return 
type. (Note that constructors are always named 'this')
sort_ex.d(35,50): Error: semicolon expected to close alias 
declaration
sort_ex.d(35,50): Error: Declaration expected, not '=>'

> auto sortBy(extractors..., R)(R r) {
>     alias preds = staticMap!(makePredicate, extractors);
>     return r.sort!preds;
> }

and this as

sort_ex.d(37,6): Error: template sort_ex.sortBy(xtors..., R)(R r) 
template tuple parameter must be last one