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Bug 17741 – std.range.transposed does not work with Map

Status: RESOLVED
Resolution: WONTFIX
Severity: enhancement
Priority: P1
Component: phobos
Product: D
Version: D2
Platform: All
OS: All
Creation time: 2017-08-10T23:30:55Z
Last change time: 2017-10-26T15:55:43Z
Assigned to: No Owner
Creator: Vladimir Panteleev

Comments

Comment #0 by dlang-bugzilla — 2017-08-10T23:30:55Z

auto ror = 5.iota.map!(y => 5.iota.map!(x => x * y)); auto result = ror.transposed; Error: template std.range.transposed cannot deduce function from argument types !()(MapResult!(__lambda1, Result)), candidates are:

Comment #1 by razvan.nitu1305 — 2017-10-25T12:19:18Z

What should be the solution here? Implement an overload which accepts a range with non-assignable elements and returns a range with non-assignable elements or offer the illusion of assign-ability by implementing a hashtable on top of transpose which tracks the changes performed in the initial range?

Comment #2 by alexandru.razvan.c — 2017-10-26T13:45:44Z

Created a PR for this. I had to change a test for issue #8764 https://issues.dlang.org/show_bug.cgi?id=8764 However I checked and it's not introducing any regression.

Comment #3 by alexandru.razvan.c — 2017-10-26T13:46:02Z

https://github.com/dlang/phobos/pull/5810

Comment #4 by alexandru.razvan.c — 2017-10-26T15:55:43Z

Decided to close this issue. The simple workaround is to use: auto result = ror.array.transposed;