Trouble using 'sort'

[Bahman Movaqar via Digitalmars-d-learn]

On 07/26/2016 09:35 AM, Bahman Movaqar wrote:
> I have a range which is the result of a couple of chained range
> operations, and each element is:
> 
>     Tuple!(string, "product", double, "price")
> 
> Now I'd like to sort the range by "price" using:
> 
>     sort!((pp1, pp2) => cmp(pp1.price,  pp2.price) > 0)(theRange)
> 
> But I get a compile time error:
> 
> source/services.d(166,63): Error: template std.algorithm.sorting.sort
> cannot deduce function from argument types !((pp1, pp2) =>
> cmp(pp1.price, pp2.price) > 0)(MapResult!(__lambda5, Result)),
> candidates are:
> /home/bahman/Programs/D/dmd-2.071.0/linux/bin64/../../src/phobos/std/algorithm/sorting.d(1027,1):
>        std.algorithm.sorting.sort(alias less = "a < b", SwapStrategy ss
> = SwapStrategy.unstable, Range)(Range r) if ((ss ==
> SwapStrategy.unstable && (hasSwappableElements!Range ||
> hasAssignableElements!Range) || ss != SwapStrategy.unstable &&
> hasAssignableElements!Range) && isRandomAccessRange!Range &&
> hasSlicing!Range && hasLength!Range)
> source/services.d(168,5): Error: var has no effect in expression (theRange)
> dmd failed with exit code 1.

Alright...further experiments.  The following works:

    sort!((pp1, pp2) => cmp(pp1.price,  pp2.price) > 0)(theRange)

So it may be something about what kind of range I'm passing to `sort`.
Am I right?

-- 
Bahman