add .head as syntax extension to AtLeast2[List, *]

gerlichlab · Oct 26, 2024 · bf6a262 · bf6a262
1 parent 0a59b37
commit bf6a262
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diff --git a/modules/pan/src/main/scala/collections.scala b/modules/pan/src/main/scala/collections.scala
@@ -101,6 +101,9 @@ object collections:
           */
         def contains(x: X): Boolean = (xs: List[X]).contains(x)
 
+        /** Access the first element of the collection. */
+        def head: X = (xs: List[X]).head
+
         /** We can safely convert to [[cats.data.NonEmptyList]]. */
         def toNel: NonEmptyList[X] = NonEmptyList(xs.head, xs.tail)
 

diff --git a/modules/pan/src/test/scala/TestAtLeast2.scala b/modules/pan/src/test/scala/TestAtLeast2.scala
@@ -75,4 +75,9 @@ class TestAtLeast2 extends AnyFunSuite, ScalaCheckPropertyChecks, should.Matcher
       "import AtLeast2.syntax.map; AtLeast2.unsafe(List(0, 1, 2)).map(_ + 1): AtLeast2[List, Int]"
     ) // With the proper syntax import, the .map operation works.
 
+  test("Wrapping a list in the AtLeast2 refinement doesn't change the .head element."):
+    import AtLeast2.syntax.head
+    forAll: (x: Int, xs: NonEmptyList[Int]) =>
+      AtLeast2(x, xs).head shouldEqual x
+
 end TestAtLeast2