doc clarifications (PR 9307) and arity issue (PR 9025)

svn: r9855

collects/mzlib/scribblings/thread.scrbl

@@ -65,10 +65,7 @@ it is still running, leaving the coroutine result unchanged.}
          (values thread? procedure?)]{
 
 Returns two values: a thread descriptor for a new thread, and a
-procedure with the same arity as @scheme[f]. (The returned procedure
+procedure with the same arity as @scheme[f].
-actually accepts any number of arguments, but immediately raises
-@scheme[exn:fail:contract:arity] if @scheme[f] cannot accept the
-provided number of arguments.)
 
 When the returned procedure is applied, its arguments are queued to be
 passed on to @scheme[f], and @|void-const| is immediately returned.

collects/mzlib/thread.ss

@@ -41,18 +41,13 @@
           (lambda ()
             (init)
             (loop))))
-       (lambda new-state
+       (procedure-reduce-arity
-         (let ([num (length new-state)])
+        (lambda new-state
-           (unless (procedure-arity-includes? f num)
+          (semaphore-wait protect)
-             (raise
+          (set! front-state (cons new-state front-state))
-              (make-exn:fail:contract:arity
+          (semaphore-post protect)
-               (format "<procedure-from-consumer-thread>: consumer procedure arity is ~e; provided ~s argument~a"
+          (semaphore-post sema))
-                       (procedure-arity f) num (if (= 1 num) "" "s"))
+        (procedure-arity f)))))
-               (current-continuation-marks)))))
-         (semaphore-wait protect)
-         (set! front-state (cons new-state front-state))
-         (semaphore-post protect)
-         (semaphore-post sema)))))
 
   (define/kw (run-server port-number handler connection-timeout
                          #:optional

collects/scribblings/reference/cont-marks.scrbl

@@ -121,19 +121,26 @@ Returns @scheme[#t] if @scheme[v] is a mark set created by
           [mark-set continuation-mark-set?])
           list?]{
 
-Returns a list representing a ``@index["stack dump"]{@as-index{stack
+Returns a list representing an approximate ``@index["stack
-trace}}'' for @scheme[mark-set]'s continuation. The list contains
+dump"]{@as-index{stack trace}}'' for @scheme[mark-set]'s
-pairs, where the @scheme[car] of each pair contains either @scheme[#f]
+continuation. The list contains pairs, where the @scheme[car] of each
-or a symbol for a procedure name, and the @scheme[cdr] of each pair
+pair contains either @scheme[#f] or a symbol for a procedure name, and
-contains either @scheme[#f] or a @scheme[srcloc] value for the
+the @scheme[cdr] of each pair contains either @scheme[#f] or a
-procedure's source location (see @secref["linecol"]); the
+@scheme[srcloc] value for the procedure's source location (see
-@scheme[car] and @scheme[cdr] are never both @scheme[#f].
+@secref["linecol"]); the @scheme[car] and @scheme[cdr] are never both
+@scheme[#f].
 
-The stack-trace list is the result of
+Conceptually, the stack-trace list is the result of
 @scheme[continuation-mark-set->list] with @scheme[mark-set] and
-Scheme's private key for procedure-call marks. A stack trace is
+Scheme's private key for procedure-call marks. The implementation may
-extracted from an exception and displayed by the default error display
+be different, however, and the results may merely approximate the
-handler (see @scheme[current-error-display-handler]) for exceptions other than
+correct answer. Thus, while the result may contain useful hints to
+humans about the context of an expression, it is not reliable enough
+for programmatic use.
+
+A stack trace is extracted from an exception and displayed by the
+default error display handler (see
+@scheme[current-error-display-handler]) for exceptions other than
 @scheme[exn:fail:user] (see @scheme[raise-user-error] in
 @secref["errorproc"]).}