dylan: Fix return value of push-last

According to the DRM, the push-last function is supposed to return the
new value added to a deque rather than the deque.

* sources/dylan/deque.dylan
  (trusted-push-last): Change to return the new element.
  (push-last): Change return signature to reflect returning
   the new element.

* sources/dylan/tests/collections.dylan
  (test test-<deque>-functions): New test (inspired by cmu-test-suite)
   for testing <deque>-specific functions and methods.
  (suite dylan-collections-test-suite): Add test-<deque>-functions.

sources/dylan/deque.dylan

@@ -517,7 +517,7 @@ end method pop;
 //
 
 define sealed inline method trusted-push-last
-    (deque :: <object-deque>, new-element) => (result :: <deque>)
+    (deque :: <object-deque>, new-element) => (new-element)
   let rep = deque.representation;
   let rep-last-index = rep.last-index;
   while (rep-last-index = (rep.size - 1))
@@ -529,13 +529,13 @@ define sealed inline method trusted-push-last
   end while;
   rep.last-index := rep-last-index := rep-last-index + 1;
   island-deque-element(rep, rep-last-index) := new-element;
-  deque
+  new-element
 end method trusted-push-last;
 
 define sealed method push-last
-    (deque :: <object-deque>, new-element) => (result :: <deque>)
+    (deque :: <object-deque>, new-element) => (new-element)
   check-type(new-element, element-type(deque));
-  trusted-push-last(deque, new-element);
+  trusted-push-last(deque, new-element)
 end method push-last;
 
 

sources/dylan/tests/collections.dylan

@@ -62,6 +62,22 @@ define test test-<deque> ()
     test-collection-class(<deque>, instantiable?: #t);
 end;
 
+define test test-<deque>-functions ()
+  let d = make-test-instance(<deque>);
+  for (i from 5 to 1 by -1)
+    check-equal("push returns new value", i, push(d, i));
+  end for;
+  for (i from 6 to 10)
+    check-equal("push-last returns new value", i, push-last(d, i));
+  end for;
+  check-equal("first pop is last item inserted at start", 1, pop(d));
+  check-equal("first pop-lat is last item inserted at end", 10, pop-last(d));
+  check-true("add! returns <deque> argument", d == add!(d, 1));
+  check-equal("add! added new element to front", 1, pop(d));
+  check-true("remove! returns <deque> argument", d == remove!(d, 9));
+  check-equal("remove! removed final element", 8, pop-last(d));
+end;
+
 define test test-<list> ()
     test-collection-class(<list>, instantiable?: #t);
 end;
@@ -108,6 +124,7 @@ define suite dylan-collections-test-suite ()
   test test-<simple-object-vector>;
   test test-<stretchy-vector>;
   test test-<deque>;
+  test test-<deque>-functions;
   test test-<list>;
   test test-<pair>;
   test test-<empty-list>;