Functions and closures

Ret name(Type1 p1, Type2 p2 = default) { body }

• The return type comes first. Void functions return nothing.
• Parameters are immutable bindings. Defaults must be pure compile-time expressions; callers may pass arguments by name (f(1, p2 = 3)).
• Arguments must match parameter types exactly after literal adoption.
• pub exports a function from its module.
• @requires(caps) before a function grants it capabilities (Capabilities).
• Int main() is the program’s entry point; its result is the exit status.

A call in tail position compiles to a jump, so tail recursion runs in constant stack space.

Closures

A closure type is written R closure(P1, P2), where R may be any type (List(Str) closure(Str)); a lambda builds one:

Int closure(Int, Int) add = lambda(a, b) { a + b };

• A lambda’s parameter types come from the expected closure type: a typed binding, a parameter, or the enclosing function’s return type.
• A lambda captures the values it names (numbers, strings, lists, maps, records, sums and other closures). Values are immutable, so a capture is a copy of a value, never a shared variable.
• A Void closure runs its body for effect and discards its value.
• The capabilities a lambda’s body needs belong to the function that writes the lambda.