fixes #1399: add fold and syntax. (#1408)

zio · Nov 10, 2024 · b4669b5 · b4669b5
1 parent cefbab3
commit b4669b5
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diff --git a/core-tests/shared/src/test/scala/zio/prelude/ForEachSpec.scala b/core-tests/shared/src/test/scala/zio/prelude/ForEachSpec.scala
@@ -99,6 +99,13 @@ object ForEachSpec extends ZIOBaseSpec {
             assert(actual)(equalTo(expected))
           }
         },
+        test("fold") {
+          check(genList) { as =>
+            val actual   = ForEach[List].fold(as.map(newtypes.Sum(_)))
+            val expected = as.sum
+            assert(actual)(equalTo(expected))
+          }
+        },
         test("foldLeft") {
           check(genList, genInt, genIntFunction2) { (as, s, f) =>
             val actual   = ForEach[List].foldLeft(as)(s)(f)

diff --git a/core/shared/src/main/scala/zio/prelude/ForEach.scala b/core/shared/src/main/scala/zio/prelude/ForEach.scala
@@ -494,6 +494,8 @@ trait ForEachSyntax {
       F.filterM(self)(f)
     def find(f: A => Boolean)(implicit F: ForEach[F]): Option[A]                                                =
       F.find(self)(f)
+    def fold(implicit F: ForEach[F], I: Identity[A]): A                                                         =
+      F.fold(self)
     def foldLeft[S](s: S)(f: (S, A) => S)(implicit F: ForEach[F]): S                                            =
       F.foldLeft(self)(s)(f)
     def foldLeftM[G[+_]: IdentityFlatten: Covariant, S](s: S)(f: (S, A) => G[S])(implicit F: ForEach[F]): G[S]  =