Simplify $guard & $reset-protect using call-in-continuation (#904)

Author: mnieper

s/7.ss

@@ -1,12 +1,12 @@
 ;;; 7.ss
 ;;; Copyright 1984-2017 Cisco Systems, Inc.
-;;; 
+;;;
 ;;; Licensed under the Apache License, Version 2.0 (the "License");
 ;;; you may not use this file except in compliance with the License.
 ;;; You may obtain a copy of the License at
-;;; 
+;;;
 ;;; http://www.apache.org/licenses/LICENSE-2.0
-;;; 
+;;;
 ;;; Unless required by applicable law or agreed to in writing, software
 ;;; distributed under the License is distributed on an "AS IS" BASIS,
 ;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
@@ -466,7 +466,7 @@
     (define-record-type (sstats make-sstats sstats?)
       (nongenerative #{sstats pfwch3jd8ts96giujpitoverj-0})
       (sealed #t)
-      (fields 
+      (fields
         (mutable cpu sstats-cpu set-sstats-cpu!)
         (mutable real sstats-real set-sstats-real!)
         (mutable bytes sstats-bytes set-sstats-bytes!)
@@ -479,7 +479,7 @@
           (lambda (cpu real bytes gc-count gc-cpu gc-real gc-bytes)
             (new cpu real bytes gc-count gc-cpu gc-real gc-bytes))))))
   (define exact-integer? (lambda (x) (and (integer? x) (exact? x))))
-  (set-who! make-sstats 
+  (set-who! make-sstats
     (lambda (cpu real bytes gc-count gc-cpu gc-real gc-bytes)
       (define verify-time
         (lambda (name x)
@@ -616,29 +616,26 @@
      (unless (and (real? v) (not (negative? v)))
        ($oops 'collect-maximum-generation-threshold-factor "~s is not a nonnegative real" v))
      v)))
-  
+
 (define $reset-protect
   (lambda (body out)
-    ((call/cc
-       (lambda (k)
-         (parameterize ([reset-handler
+    (call/cc
+      (lambda (k)
+        (parameterize ([reset-handler
                          (lambda ()
-                           (k (lambda ()
-                                (out)
-                                ((reset-handler)))))])
-           (with-exception-handler
-             (lambda (c)
-              ; would prefer not to burn bridges even for serious condition
-              ; if the exception is continuable, but we have no way to know
-              ; short of grubbing through the continuation
-               (if (serious-condition? c)
-                   (k (lambda () (out) (raise c)))
-                   (raise-continuable c)))
-             (lambda ()
-               (call-with-values body
-                 (case-lambda
-                   [(v) (lambda () v)]
-                   [v* (lambda () (apply values v*))]))))))))))
+                           (call-in-continuation k
+                             (lambda ()
+                               (out)
+                               ((reset-handler)))))])
+          (with-exception-handler
+              (lambda (c)
+               ; would prefer not to burn bridges even for serious condition
+               ; if the exception is continuable, but we have no way to know
+               ; short of grubbing through the continuation
+                (if (serious-condition? c)
+                    (call-in-continuation k (lambda () (out) (raise c)))
+                    (raise-continuable c)))
+            body))))))
 
 (define exit-handler)
 (define reset-handler)
@@ -890,7 +887,7 @@
         (docollect
           (lambda (gct prev-allocated-after-max)
             (let ([max-gen? (fx= g (collect-maximum-generation))])
-              (values 
+              (values
                ; make gc-trip to look like we've just collected generation g
                ; w/o also having collected generation g+1
                (if max-gen?
@@ -1288,7 +1285,7 @@
                  (condition-wait $collect-cond $tc-mutex)
                  (f)]))))
         (critical-section
-          (dynamic-wind 
+          (dynamic-wind
             once
             (collect-request-handler)
             (lambda () (set! $collect-request-pending #f))))))))
@@ -1467,7 +1464,7 @@
   (define-record-type pass-stats
     (nongenerative)
     (sealed #t)
-    (fields 
+    (fields
       (mutable calls)
       (mutable cpu)
       (mutable gc-cpu)
@@ -1489,7 +1486,7 @@
       (set! stats-ht (make-eq-hashtable))))
 
   (set! $enable-pass-timing (make-parameter #f))
-  
+
   (set-who! $pass-time
     (lambda (name thunk)
       (unless (symbol? name) ($oops who "~s is not a symbol" name))
@@ -1539,8 +1536,8 @@
       (define (build-result namev psv)
         (vector->list
           (vector-map
-            (lambda (name ps) 
-              (list name 
+            (lambda (name ps)
+              (list name
                 (pass-stats-calls ps)
                 (pass-stats-cpu ps)
                 (pass-stats-gc-cpu ps)

s/exceptions.ss

@@ -1,12 +1,12 @@
 ;;; exceptions.ss
 ;;; Copyright 1984-2017 Cisco Systems, Inc.
-;;; 
+;;;
 ;;; Licensed under the Apache License, Version 2.0 (the "License");
 ;;; you may not use this file except in compliance with the License.
 ;;; You may obtain a copy of the License at
-;;; 
+;;;
 ;;; http://www.apache.org/licenses/LICENSE-2.0
-;;; 
+;;;
 ;;; Unless required by applicable law or agreed to in writing, software
 ;;; distributed under the License is distributed on an "AS IS" BASIS,
 ;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
@@ -94,7 +94,7 @@ TODO:
           [(message-condition? c)
            (let ([irritants (if (irritants-condition? c) (condition-irritants c) '())])
              (case (and (list? irritants) (length irritants))
-               [(0) 
+               [(0)
                 ($report-string op
                   (and prefix? (if (warning-only? c) "warning" "exception"))
                   (and (who-condition? c) (condition-who c))
@@ -263,37 +263,27 @@ TODO:
   (set-who! $guard
     (lambda (supply-else? guards body)
       (if supply-else?
-          ((call/cc
-             (lambda (kouter)
-               (let ([original-handler-stack ($current-handler-stack)])
-                 (with-exception-handler
-                   (lambda (arg)
-                     ((call/cc
+          (call/cc
+            (lambda (kouter)
+              (let ([original-handler-stack ($current-handler-stack)])
+                (with-exception-handler
+                    (lambda (arg)
+                      (call/cc
                         (lambda (kinner)
-                          (kouter
+                          (call-in-continuation kouter
                             (lambda ()
                               (guards arg
                                 (lambda ()
-                                  (kinner
+                                  (call-in-continuation kinner
                                     (lambda ()
                                       (parameterize ([$current-handler-stack original-handler-stack])
-                                        (raise-continuable arg))))))))))))
-                   (lambda ()
-                     (call-with-values
-                       body
-                       (case-lambda
-                         [(x) (lambda () x)]
-                         [vals (lambda () (apply values vals))]))))))))
-          ((call/cc
-             (lambda (k)
-               (with-exception-handler
-                 (lambda (arg) (k (lambda () (guards arg))))
-                 (lambda ()
-                   (call-with-values
-                     body
-                     (case-lambda
-                       [(x) (lambda () x)]
-                       [vals (lambda () (apply values vals))]))))))))))
+                                        (raise-continuable arg)))))))))))
+                  body))))
+          (call/cc
+            (lambda (k)
+              (with-exception-handler
+                  (lambda (arg) (call-in-continuation k (lambda () (guards arg))))
+                body))))))
 )
 
 (define-syntax guard
@@ -471,7 +461,7 @@ TODO:
 ;;; defining its child types, even though the system is compiled with
 ;;; (eval-syntax-expanders-when) not including compile.
 (begin
-(let-syntax ([a (syntax-rules () 
+(let-syntax ([a (syntax-rules ()
                   [(_ &condition) ; leave only &condition visible
                    (define-record-type (&condition make-simple-condition simple-condition?)
                      (nongenerative #{&condition oyb459ue1fphfx4-a}))])])
@@ -706,7 +696,7 @@ TODO:
       (for-each
         (lambda (m) (unless (string? m) ($oops who "~s is not a string" m)))
         messages)
-      (error-help #f who #f 
+      (error-help #f who #f
         (if (null? messages) "invalid syntax" (apply string-append messages))
         #f (make-syntax-violation form #f))))