Add min/max overloads with comparison functions (#23595)

`min`, `max`, `minmax`, `minIndex` and `maxIndex`

changelog.md

@@ -34,7 +34,7 @@ errors.
 [//]: # "Changes:"
 
 - `std/math` The `^` symbol now supports floating-point as exponent in addition to the Natural type.
-
+- `min`, `max`, and `sequtils`' `minIndex`, `maxIndex` and `minmax` for `openArray`s now accept a comparison function.
 - `system.substr` implementation now uses `copymem` (wrapped C `memcpy`) for copying data, if available at compilation.
 - `system.newStringUninit` is now considered free of side-effects allowing it to be used with `--experimental:strictFuncs`.
 

lib/pure/collections/sequtils.nim

@@ -231,6 +231,18 @@ func deduplicate*[T](s: openArray[T], isSorted: bool = false): seq[T] =
       for itm in items(s):
         if not result.contains(itm): result.add(itm)
 
+proc min*[T](x: openArray[T], cmp: proc(a, b: T): int): T {.effectsOf: cmp.} =
+  ## The minimum value of `x`.
+  result = x[0]
+  for i in 1..high(x):
+    if cmp(x[i], result) < 0: result = x[i]
+
+proc max*[T](x: openArray[T], cmp: proc(a, b: T): int): T {.effectsOf: cmp.} =
+  ## The maximum value of `x`.
+  result = x[0]
+  for i in 1..high(x):
+    if cmp(result, x[i]) < 0: result = x[i]
+
 func minIndex*[T](s: openArray[T]): int {.since: (1, 1).} =
   ## Returns the index of the minimum value of `s`.
   ## `T` needs to have a `<` operator.
@@ -248,6 +260,20 @@ func minIndex*[T](s: openArray[T]): int {.since: (1, 1).} =
   for i in 1..high(s):
     if s[i] < s[result]: result = i
 
+func minIndex*[T](s: openArray[T], cmp: proc(a, b: T): int): int {.effectsOf: cmp.} =
+  ## Returns the index of the minimum value of `s`.
+  runnableExamples:
+    import std/sugar
+
+    let s1 = @["foo","bar", "hello"]
+    let s2 = @[2..4, 1..3, 6..10]
+    assert minIndex(s1, proc (a, b: string): int = a.len - b.len) == 0
+    assert minIndex(s2, (a, b) => a.a - b.a) == 1
+
+  for i in 1..high(s):
+    if cmp(s[i], s[result]) < 0: result = i
+
+
 func maxIndex*[T](s: openArray[T]): int {.since: (1, 1).} =
   ## Returns the index of the maximum value of `s`.
   ## `T` needs to have a `<` operator.
@@ -265,15 +291,35 @@ func maxIndex*[T](s: openArray[T]): int {.since: (1, 1).} =
   for i in 1..high(s):
     if s[i] > s[result]: result = i
 
+func maxIndex*[T](s: openArray[T], cmp: proc(a, b: T): int): int {.effectsOf: cmp.} =
+  ## Returns the index of the maximum value of `s`.
+  runnableExamples:
+    import std/sugar
+
+    let s1 = @["foo","bar", "hello"]
+    let s2 = @[2..4, 1..3, 6..10]
+    assert maxIndex(s1, proc (a, b: string): int = a.len - b.len) == 2
+    assert maxIndex(s2, (a, b) => a.a - b.a) == 2
+
+  for i in 1..high(s):
+    if cmp(s[result], s[i]) < 0: result = i
+
 func minmax*[T](x: openArray[T]): (T, T) =
   ## The minimum and maximum values of `x`. `T` needs to have a `<` operator.
   var l = x[0]
   var h = x[0]
   for i in 1..high(x):
     if x[i] < l: l = x[i]
-    if h < x[i]: h = x[i]
+    elif h < x[i]: h = x[i]
   result = (l, h)
 
+func minmax*[T](x: openArray[T], cmp: proc(a, b: T): int): (T, T) {.effectsOf: cmp.} =
+  ## The minimum and maximum values of `x`.
+  result = (x[0], x[0])
+  for i in 1..high(x):
+    if cmp(x[i], result[0]) < 0: result[0] = x[i]
+    elif cmp(result[1], x[i]) < 0: result[1] = x[i]
+
 
 template zipImpl(s1, s2, retType: untyped): untyped =
   proc zip*[S, T](s1: openArray[S], s2: openArray[T]): retType =