utils.lisp

   1
   2 (in-package :lambdamundo)
   3
   4 (defmacro with-gensyms ((&rest names) &body body)
   5   `(let ,(loop for n in names collect `(,n (gensym)))
   6      ,@body))
   7
   8 (defmacro once-only ((&rest names) &body body)
   9   (let ((gensyms (loop for n in names collect (gensym))))
  10     `(let (,@(loop for g in gensyms collect `(,g (gensym))))
  11        `(let (,,@(loop for g in gensyms for n in names collect ``(,,g ,,n)))
  12           ,(let (,@(loop for n in names for g in gensyms collect `(,n ,g)))
  13              ,@body)))))
  14
  15 (defmacro when-funcall (x &rest parameters)
  16   "If the first argument is not NIL, assume it's a function and call
  17 it with the supplied parameters."
  18   (with-gensyms (fun)
  19     `(let ((,fun ,x))
  20        (when ,fun
  21          (funcall ,fun ,@parameters)))))