Simple localscope in TXR Lisp: $ txr -i localscope.tl Pour le service en la langue Shell, appuyez sur Ctrl-D. 1> (localscope (+ %pi% %pi%)) ;; OK, %pi% i

Simple localscope in TXR Lisp: $ txr -i localscope.tl Pour le service en la langue Shell, appuyez sur Ctrl-D. 1> (localscope (+ %pi% %pi%)) ;; OK, %pi% is built-in 6.28318530717959 2> (localscope *print-base*) ;; likewise 10 3> (localscope (+ a b c)) ;; bad ** expr-3:1: localscope: global variables (c b a) used Code: (defmacro localscope (:form f :env e . forms) (let ((body ^(progn ,*forms))) (tree-bind (exp fv-inner ff-inner fv-outer ff-outer) (expand-with-free-refs body e) (ignore ff-inner fv-outer ff-outer) (let* ((usr (find-package :usr)) (globals [keep-if (do or (not (boundp @1)) (neq (symbol-package @1) usr)) fv-inner])) (if globals (compile-error f "global variables ~s used" globals))) body))) We get a list of the free variable references emanating from the enclosed forms, and filter them: we are interested in all that do not have bindings as globals in the standard library. I.e. either are not bound at all, or else if they are, are not symbols in the usr: ("user space") package.