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original commit: 2d30c43545cf26b9c25558e646dd3d658269c1b9
23 years ago · f60e3ba1e2
parent d7837cf5b7
commit f60e3ba1e2
1 changed files with 5 additions and 3 deletions
--- a/collects/parser-tools/private-yacc/parser-builder.ss
+++ b/collects/parser-tools/private-yacc/parser-builder.ss
@ -29,9 +29,11 @@
                                  (map syntax->list 
                                       (syntax->list (syntax (((bound ...) ...) ...)))))))))
             (terms (get-term-list terms))
-             (precs (syntax-case precs ()
-                      ((_ (__ term ...) ...)
-                       (apply append (map syntax->list (syntax->list (syntax ((term ...) ...)))))))))
+             (precs (if precs
+                        (syntax-case precs ()
+                          ((_ (__ term ...) ...)
+                           (apply append (map syntax->list (syntax->list (syntax ((term ...) ...)))))))
+                        null)))
         `(if #f (let ,(map (lambda (bind)
                              `(,(strip bind) void))
                            (append terms binds))