toLower
Nick Treleaven
nick at geany.org
Fri Aug 18 11:04:30 UTC 2023
On Thursday, 17 August 2023 at 09:28:05 UTC, Joel wrote:
> .map!(std.uni.toLower)
> .sort!"a<b"
> .writeln;
> }
> ```
> onlineapp.d(8): Error: none of the overloads of template
> `std.algorithm.sorting.sort` are callable using argument types
> `!("a<b")(MapResult!(toLower, ByCodeUnitImpl))`
>
> /dlang/dmd/linux/bin64/../../src/phobos/std/algorithm/sorting.d(1925): Candidate is: `sort(alias less = "a < b", SwapStrategy ss = SwapStrategy.unstable, Range)(Range r)`
> with `less = "a<b",
> ss = SwapStrategy.unstable,
> Range = MapResult!(toLower, ByCodeUnitImpl)`
> must satisfy one of the following constraints:
> ` hasSwappableElements!Range
> hasAssignableElements!Range
> ss != SwapStrategy.unstable`
`map` generates a range `r` whose elements can be accessed by
mutable reference only if the result of calling the map function
(on a source element) is a mutable reference. But
`std.uni.toLower` returns by value, and `sort` requires `r.front`
to be a mutable reference.
I'll look at improving the docs.
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