add hygienic `or` syntax

2013-12-09 15:37:29 +09:00 · 2013-12-09 15:37:29 +09:00 · daae383938
parent 3c6fd93b5a
commit daae383938
1 changed files with 11 additions and 0 deletions
--- a/piclib/built-in.scm
+++ b/piclib/built-in.scm
@ -611,6 +611,17 @@
        (identifier=? use-env x use-env y))
      (make-syntactic-closure mac-env '() (unwrap (f (wrap expr) inject compare))))))

+(define-syntax or
+  (er-macro-transformer
+   (lambda (expr inject compare)
+     (let ((exprs (cdr expr)))
+       (if (null? exprs)
+           #f
+           `(let ((it ,(car exprs)))
+              (if it
+                  it
+                  (or ,@(cdr exprs)))))))))
+
 (define-syntax case
  (er-macro-transformer
   (lambda (expr inject compare)