chore: cleanup

docs/writeups/0009-closures.md

@@ -0,0 +1,43 @@
+# WU0009: Closures
+
+## Syntax
+
+```rust
+// look at previous writeup regarding switches?
+pattern := identifier | '(' pattern [ ',' pattern ]* ')'
+closure := pattern '->' expr
+```
+
+## Tuples as argument lists
+
+## How to pass closures as arguments?
+## How should function arguments look like?
+
+```rust
+func map[T, U](value: Maybe[T], f: Func[(T), U]) -> Maybe[U] {
+    switch value {
+        Nothing => Nothing,
+        inner: T => f(inner),
+    }
+}
+```
+
+## How to capture variables?
+
+### Issues?
+### design consideration?
+### generalize to functions
+
+## Code examples
+
+```rust
+where values = [1, 2, 3];
+
+values
+  .map(elt -> elt * 2)
+  .zip()
+  .for_each((i, elt) -> println("value at {i}: {elt}"))
+  // or
+  .for_each(tup -> println("value at {tup[0]}: {tup[1]}"))
+```
+