Seq.sortBy

CHANGELOG.md

@@ -1,7 +1,9 @@
-## Version 1.0.1
+## Version 1.1.0
 
 - Fix bug in `allPairs` where sequences are not cached.
 - `Seq.reverse`
+- `Seq.sortBy`
+- `Seq.delay`
 
 ## Version 1.0.0
 

SEQ_README.md

@@ -78,6 +78,7 @@ let pairwise: t<'a> => t<('a, 'a)>
 let reverse: t<'a> => t<'a>
 let scan: (t<'a>, 'b, ('b, 'a) => 'b) => t<'b>
 let scani: (t<'a>, ~zero: 'b, (~sum: 'b, ~val: 'a, ~inx: int) => 'b) => t<'b>
+let sortBy: (t<'a>, ('a, 'a) => int) => t<'a>
 let takeAtMost: (t<'a>, int) => t<'a>
 let takeUntil: (t<'a>, 'a => bool) => t<'a>
 let takeWhile: (t<'a>, 'a => bool) => t<'a>

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@jmagaram/rescript-extras",
-  "version": "1.0.1",
+  "version": "1.1.0",
   "module": "",
   "description": "Useful general-purpose utility functions and modules for ReScript projects.",
   "keywords": [

src/Extras__Seq.res

@@ -706,3 +706,10 @@ let reverse = xx =>
     | _ => xx->fromArray(~start=xx->Js.Array2.length - 1, ~end=0)
     }
   })
+
+let sortBy = (xx, compare) =>
+  delay(() => {
+    let xx = xx->toArray
+    xx->Js.Array2.sortInPlaceWith(compare)->ignore
+    xx->fromArray
+  })

src/Extras__Seq.resi

@@ -646,3 +646,11 @@ let reverse: t<'a> => t<'a>
 sequence.
 */
 let delay: (unit => t<'a>) => t<'a>
+
+/**
+`sortBy(source, compare)` consumes the entire `source` sequence as soon as that
+sequence is iterated. As such it should not be used with large or infinite
+sequences. The function uses a stable sort (the original order of equal elements
+is preserved) based on the provided `compare` function.
+*/
+let sortBy: (t<'a>, ('a, 'a) => int) => t<'a>

tests/Extras__SeqTests.res

@@ -6,6 +6,7 @@ module Option = Belt.Option
 module Result = Belt.Result
 
 let intToString = Belt.Int.toString
+let intCompare = Ex.Cmp.int
 
 let concatInts = xs =>
   xs->Js.Array2.length == 0 ? "_" : xs->Js.Array2.map(intToString)->Js.Array2.joinWith("")
@@ -1578,13 +1579,54 @@ let orElseTests = makeSeqEqualsTests(
   ],
 )
 
+let sortByTests = makeSeqEqualsTests(
+  ~title="sortBy",
+  [
+    (S.empty->S.sortBy(intCompare), [], ""),
+    (S.singleton(1)->S.sortBy(intCompare), [1], ""),
+    ([1, 5, 2, 9, 7, 3]->S.fromArray->S.sortBy(intCompare), [1, 2, 3, 5, 7, 9], ""),
+  ],
+)->Js.Array2.concat([
+  T.make(~category="Seq", ~title="sortBy", ~expectation="completely lazy", ~predicate=() => {
+    S.repeatWith(3, () => {Js.Exn.raiseError("boom!")})
+    ->S.sortBy(intCompare)
+    ->S.takeAtMost(0)
+    ->S.consume
+    ->ignore
+    true
+  }),
+  T.make(~category="Seq", ~title="sortBy", ~expectation="stable", ~predicate=() => {
+    let sortByFirst = (a, b) => {
+      let (afst, _) = a
+      let (bfst, _) = b
+      intCompare(afst, bfst)
+    }
+    let data = [
+      (2, "x"),
+      (1, "x"),
+      (2, "y"),
+      (4, "x"),
+      (3, "x"),
+      (1, "y"),
+      (3, "y"),
+      (2, "z"),
+      (4, "y"),
+      (1, "z"),
+      (3, "z"),
+      (4, "z"),
+    ]
+    let sorted = data->S.fromArray->S.sortBy(sortByFirst)->S.map(((_, letter)) => letter)->S.toArray
+    sorted == "xyzxyzxyzxyz"->Js.String2.split("")
+  }),
+])
+
 let delayTests = makeSeqEqualsTests(
   ~title="delay",
   [
     (S.delay(() => S.empty), [], ""),
     (S.delay(() => S.singleton(1)), [1], ""),
     (S.delay(() => oneToFive), [1, 2, 3, 4, 5], ""),
-    (S.delay(() => Js.Exn.raiseError("Boom!"))->S.takeAtMost(0), [], ""),
+    (S.delay(() => Js.Exn.raiseError("boom!"))->S.takeAtMost(0), [], ""),
   ],
 )
 
@@ -1739,6 +1781,7 @@ let tests =
     sampleZipLongest,
     scanTests,
     someTests,
+    sortByTests,
     sortedMergeTests,
     takeAtMostTests,
     takeUntilTests,