Define top-level bindings for aux syntax: else, =>, _, ...

* module/ice-9/boot-9.scm (else, =>, ..., _): New definitions.  These
  are specified by the r6rs and the r7rs.
* module/ice-9/sandbox.scm (core-bindings): Include the aux syntax
  definitions.
* module/rnrs/base.scm:
* module/rnrs.scm: Re-export aux syntax.

1 files changed, 16 insertions, 0 deletions

diff --git a/module/ice-9/boot-9.scm b/module/ice-9/boot-9.scm
index 062ab688e..f50448c0b 100644
--- a/module/ice-9/boot-9.scm
+++ b/module/ice-9/boot-9.scm
@@ -416,6 +416,22 @@ If returning early, return the return value of F."
 (define-syntax-rule (unless test stmt stmt* ...)
   (if (not test) (begin stmt stmt* ...)))
 
+(define-syntax else
+  (lambda (x)
+    (syntax-violation 'else "bad use of 'else' syntactic keyword" x x)))
+
+(define-syntax =>
+  (lambda (x)
+    (syntax-violation '=> "bad use of '=>' syntactic keyword" x x)))
+
+(define-syntax ...
+  (lambda (x)
+    (syntax-violation '... "bad use of '...' syntactic keyword" x x)))
+
+(define-syntax _
+  (lambda (x)
+    (syntax-violation '_ "bad use of '_' syntactic keyword" x x)))
+
 (define-syntax cond
   (lambda (whole-expr)
     (define (fold f seed xs)