added new safe-ops file that may be used instead of ops to disable unsafety

collects/racket/unsafe/safe-ops.rkt

@@ -0,0 +1,25 @@
+#lang racket
+
+(require racket/fixnum
+         racket/flonum)
+
+
+;; the point of this file is to provide functions that are labeled
+;; as unsafe but are actually safe.  This provides an easy means to
+;; disable unsafety; a require of racket/unsafe/ops can be replaced
+;; with a require of racket/unsafe/safe-ops. 
+
+;; this list is almost certainly incomplete; I feel partially justified
+;; in adding it to the tree anyhow because 
+;; a) it's easy to extend, and
+;; b) it appears to me (based on the require of #%unsafe in the corresponding
+;;     'ops' library) that determining the full set of functions will require
+;;     mucking around in the C source, and not being very confident about 
+;;     my conclusions.
+
+
+(provide (prefix-out unsafe- (all-from-out racket/fixnum))
+         (prefix-out unsafe- (all-from-out racket/flonum))
+         (prefix-out unsafe- (combine-out vector-length
+                                          vector-ref
+                                          vector-set!)))