maxIndex but not minIndex sometimes returns the index as an array with a single element

[dlangBugzillaToGithub]

pabuond reported this on 2024-11-13T19:28:18Z

Transfered from https://issues.dlang.org/show_bug.cgi?id=24858

CC List

• kdevel
• nick (@ntrel)
• pabuond

Description

`maxIndex` returns an array with a single element when run on an array modified by UFCS (e.g. for absolute value). `minIndex` doesn't, so I guess this is a bug.
Tested with dmd v2.109.1

```
import std.math: fabs;
import std.algorithm: minIndex, maxIndex;

double[] u = [-9, 3, 2, 8, 4];
writeln(u.maxIndex); // => 3, OK
writeln(u.map!fabs.minIndex); // => 2, OK
writeln(u.map!fabs.maxIndex); // => [0] ??? Expected: 0
```
Thanks!

[dlangBugzillaToGithub]

nick (@ntrel) commented on 2024-11-15T11:42:33Z

Are you sure? With 2.109.0 the last line does give `0`.

[dlangBugzillaToGithub]

kdevel commented on 2024-11-15T12:48:44Z

WORKSFORME

compilable version (mi.d):

```
import std.stdio : writeln;
import std.algorithm : map;
import std.math: fabs;
import std.algorithm: minIndex, maxIndex;

unittest
{
   double[] u = [-9, 3, 2, 8, 4];
   writeln(u.maxIndex); // => 3, OK
   writeln(u.map!fabs.minIndex); // => 2, OK
   writeln(u.map!fabs.maxIndex); // => [0] ??? Expected: 0
}
```

$ dmd --version
DMD64 D Compiler v2.109.1
Copyright (C) 1999-2024 by The D Language Foundation, All Rights Reserved written by Walter Bright
$ dmd -unittest -main -run mi.d 
3
2
0
1 modules passed unittests

(also works under dmd 2.098, GDC 12.1, GDC 11.3)

[dlangBugzillaToGithub]

pabuond commented on 2024-11-15T13:27:18Z

Aw, my bad - I was doing some tests, but in combination with mir.ndslice and it turns out it's due to a clash with mir.ndslice's maxIndex/minIndex that I didn't realise I was importing too. So not a bug in std.algorithm :) sorry for the false alarm! Not too sure exactly what creates the issue, some import combinations work, but one doesn't. (Of course, it's bad to import homonyms into the namespace - the compiler seemed to deal with it, so I thought it was fine, but obviously it creates some issues. There doesn't seem to be a way to use UFCS with full module names, is there?)
```
import std.stdio: writeln;
import std.math: fabs;

/* OK */
// import std.algorithm: maxIndex, minIndex, map;

/* OK */
// import std.algorithm: maxIndex, minIndex;
// import mir.ndslice: map;

/* OK */
// import std.algorithm: maxIndex, minIndex, map;
// import mir.ndslice: maxIndex, minIndex;

/* Not OK */
import std.algorithm: maxIndex, minIndex;
import mir.ndslice: maxIndex, minIndex, map;

void main()
{
	double[] u = [-9, 3, 2, 8, 4];
	writeln(u.maxIndex); // => 3, OK
	writeln(u.minIndex); // => 0, OK
	writeln(u.map!fabs.minIndex); // => [2] ???
	writeln(u.map!fabs.maxIndex); // => [0] ???
}
```