compile/decorate

Syntax: (decorate [DECORATOR ...] FORM)

Form

Expands to

(decorate [] FN)

FN

(decorate [D ...] (def NAME FORMALS BODY ...))

(var NAME (decorate [D ...] (function NAME FORMALS BODY ...)))

(decorate [D ...] (var NAME VALUE))

(var NAME (decorate [D ...] VALUE))

(decorate [D ...] (var NAME :: TYPE VALUE))

(var NAME :: TYPE (decorate [D ...] VALUE))

(decorate [D ...] (global var NAME VALUE))

(global var NAME (decorate [D ...] VALUE))

(decorate [D ...] (global var NAME :: TYPE VALUE))

(global var NAME :: TYPE (decorate [D ...] VALUE))

(decorate [D ...] (define NAME VALUE))

(var NAME (decorate [D ...] VALUE))

(decorate [D ...] (define-global NAME VALUE))

(define-global NAME (decorate [D ...] VALUE))

(decorate [D ...] (var NAME)), or any other declaration

a CompilerError, nothing to decorate

(decorate [D ...] (global def NAME FORMALS BODY ...))

(define-global NAME (decorate [D ...] (function NAME FORMALS BODY ...)))

(decorate [D ...] (global class NAME SUPERS BODY ...))

(define-global NAME (decorate [D ...] (build-class NAME SUPERS BODY ...)))

(decorate [D ...] (define [NAME FORMALS ...] BODY ...))

(var NAME (decorate [D ...] (function NAME [FORMALS ...] BODY ...)))

(decorate [D ...] (define [(NAME :: TYPE) FORMALS ...] BODY ...))

(var NAME (decorate [D ...] (function NAME :: TYPE [FORMALS ...] BODY ...)))

(decorate [D ...] (class NAME SUPERS BODY ...))

(var NAME (decorate [D ...] (build-class NAME SUPERS BODY ...)))

(decorate [D ...] (define-global [NAME FORMALS ...] BODY ...))

(define-global NAME (decorate [D ...] (function NAME [FORMALS ...] BODY ...)))

(decorate [D ...] (define-global [(NAME :: TYPE) FORMALS ...] BODY ...))

(define-global NAME (decorate [D ...] (function NAME :: TYPE [FORMALS ...] BODY ...)))

(decorate [D REST ...] FN)

(decorate-subject D (decorate [REST ...] FN))

Behaviour: What @ lines read to, and usable directly. The name of a def, var, class, global var, global def, global class, define or define-global subject is hoisted out so the decorated value is what gets bound; then the decorator list folds through decorate-subject one decorator per step, outermost first, so @d1 over @d2 over a definition applies as (d1 (d2 ...)), as in Python.

A typed value subject keeps its annotation and wraps only the value, so @d var x :: int 0 in a class body still records x in __annotations__; type: TYPE reads the same as :: TYPE. A declaration, var x, var [a b], global var x, define x or define-global x, with or without a type, binds no value, so a decorator over it has nothing to transform and the compiler raises CompilerError naming the form. A binding form of any other shape is not a declaration; it reaches its special and fails as it would undecorated, with SyntaxMatchError.

Examples:

>>> (macroexpand-1 '(decorate (d1) (def foo [x] x)))
(var foo (decorate [d1] (function foo [x] x)))

import-from functools lru_cache

@(lru_cache maxsize: None)
@demand
def fib [n]:
  if (< n 2) n (+ (fib (- n 1)) (fib (- n 2)))

The layout lines read as (decorate ((lru_cache maxsize: None) demand) (def fib ...)). See Decorators.