From 018e91979aa921edce7e27f259aa91893add7939 Mon Sep 17 00:00:00 2001
From: Callum Renwick <callum_renwick@outlook.com>
Date: Thu, 31 Dec 2020 14:25:10 +0000
Subject: [PATCH] type expressions

---
 type_expressions/main.pony | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)
 create mode 100644 type_expressions/main.pony

diff --git a/type_expressions/main.pony b/type_expressions/main.pony
new file mode 100644
index 0000000..cb6b696
--- /dev/null
+++ b/type_expressions/main.pony
@@ -0,0 +1,30 @@
+actor Main
+    new create(env: Env) =>
+        env.out.print("hlo wld")
+
+// A tuple type is a sequence of types
+var x: (String, U64)
+x = ("hi", 3)
+x = ("bye", 7)
+
+// Pony supports tuple unpacking but calls it "destructuring"
+(var y, var z) = x
+
+// You can access the elements of tuples directly using this
+// one weird syntax
+y = x._1
+z = x._2
+
+// You can't assign elements of tuples. To change the value
+// of a tuple you must reassign the whole thing.
+x = ("wibble wobble", x._2)
+
+// A union is a set of possible types
+// This means "a is a String or None":
+var a: (String | None)
+a = "yeah yeah whatever static analysis tool"
+
+// An intersection is a value that is more than one type at once
+// An example from the standard library:
+// type Map[K: (Hashable box & Comparable[K] box), V] is HashMap[K, V, HashEq[K]]
+// K is Hashable *and* Comparable[K] at the same time