records

Author: igr

flix/src/Records.flix

@@ -0,0 +1,24 @@
+/// Returns the area of the rectangle `r`.
+/// The record `r` must have `x` and `y` labels, and no other labels.
+def area2(r: {x = Int32, y = Int32}): Int32 = r.x * r.y
+
+/// Computes the area of various rectangle records.
+/// Note that the order of labels is immaterial.
+def areas(): List[Int32] =
+    area2({x = 1, y = 2}) ::
+    area2({y = 2, x = 3}) :: Nil
+
+/// Returns the area of the polymorphic record `r`.
+/// Note that the use of the type variable `a` permits the record `r`
+/// to have labels other than `x` and `y`.
+def polyArea(r : {x = Int32, y = Int32 | a}): Int32 = r.x * r.y
+
+/// Computes the area of various rectangle records.
+/// Note that some records have additional fields.
+def polyAreas(): List[Int32] =
+    polyArea({x = 1, y = 2}) ::
+    polyArea({x = 2, y = 3, z = 4}) :: Nil
+
+// def main(): Unit \ IO =
+//     areas() |> println;
+//     polyAreas() |> println