SSPUR agent spec

2-space indent, no braces or ;:

type Err = Missing{sku: Str} | Short{want: Int}

fn take(xs: List[Item], sku: Str, n: Int where _ > 0) -> List[Item] ! fail[Err]
= do
  it = xs.find(_.sku == sku).ok_or(Missing{sku})
  if n > it.qty then raise Short{want: n}
  xs.map(i => if i.sku == sku then i with qty := i.qty - n else i)

test t = catch take([], "a", 1).len == 0
  | Missing{sku} => sku == "a"
  | _ => false

• Effects after !: fail[E] (raise or a failing call), log, div (while).
• do lines: x = e, var x = e then x := e, for x in xs, while c; the last is the value. if without else is for raise.
• match e/catch e + | Pat => e arms of e’s type; a nested match indents its arms deeper. e is some(_) is a Bool; some(v) = e else d binds or ends the block.
• _ makes the innermost call argument a lambda; _ => e ignores its argument. "{x}" interpolates; \{ is a literal {. Tuples (a, b), t.0, (a, b) = e. x.f(a) calls f(x, a); x.f is a field or a zero-argument call.
• List: len map filter find fold(init, (acc, x) => e) any all sort sort_by(key) reverse sum push(x) take drop contains index_of unique enumerate join(sep) counts first last. Str: len trim split(sep) lower upper chars contains starts_with replace(a, b) take drop to_int. find first last index_of to_int give Opt: or(d) get is_some ok_or(e). Any: .str.
• Rarely needed: ./sspur spec --more (Map, Set, regex, JSON, pre/post, traits, patterns, builtins).

Edit: write whole new or changed definitions to change.ssp, then run ./sspur edit --test change.ssp in the same turn. Each definition replaces the one with its name or is added; remove NAME and rename A B lines too. Put every change in one edit; done at N passed, 0 failed.