Clean up --partition-after-pred

* dash.el (--partition-after-pred): Simplify.  Extend docstring.
(-partition-after-pred): Extend docstring.
* dev/examples.el (-partition-after-pred): Extend tests.

* README.md:
* dash.texi: Regenerate docs.

Re: #362.

README.md

@@ -1540,7 +1540,9 @@ other value (the body).
 
 #### -partition-after-pred `(pred list)`
 
-Partition directly after each time `pred` is true on an element of `list`.
+Partition `list` after each element for which `pred` returns non-nil.
+
+This function's anaphoric counterpart is `--partition-after-pred`.
 
 ```el
 (-partition-after-pred #'booleanp ()) ;; => ()

dash.el

@@ -1383,27 +1383,29 @@ other value (the body)."
   (--partition-by-header (funcall fn it) list))
 
 (defmacro --partition-after-pred (form list)
-  "Anaphoric form of `-partition-after-pred'."
-  (let ((r (make-symbol "result"))
-        (s (make-symbol "sublist"))
-        (l (make-symbol "list")))
-    `(let ((,l ,list))
+  "Partition LIST after each element for which FORM evaluates to non-nil.
+Each element of LIST in turn is bound to `it' before evaluating
+FORM.
+
+This is the anaphoric counterpart to `-partition-after-pred'."
+  (let ((l (make-symbol "list"))
+        (r (make-symbol "result"))
+        (s (make-symbol "sublist")))
+    `(let ((,l ,list) ,r ,s)
        (when ,l
-         (let* ((,r nil)
-                (,s nil))
-           (while ,l
-             (let* ((it (car ,l)))
-               (!cdr ,l)
-               (!cons it ,s)
+         (--each ,l
+           (push it ,s)
            (when ,form
-                 (!cons (nreverse ,s) ,r)
-                 (setq ,s nil))))
-           (if ,s
-	       (!cons (nreverse ,s) ,r))
-           (nreverse ,r))))))
+             (push (nreverse ,s) ,r)
+             (setq ,s ())))
+         (when ,s
+           (push (nreverse ,s) ,r))
+         (nreverse ,r)))))
 
 (defun -partition-after-pred (pred list)
-  "Partition directly after each time PRED is true on an element of LIST."
+  "Partition LIST after each element for which PRED returns non-nil.
+
+This function's anaphoric counterpart is `--partition-after-pred'."
   (--partition-after-pred (funcall pred it) list))
 
 (defun -partition-before-pred (pred list)

dash.texi

@@ -2197,7 +2197,9 @@ other value (the body).
 
 @anchor{-partition-after-pred}
 @defun -partition-after-pred (pred list)
-Partition directly after each time @var{pred} is true on an element of @var{list}.
+Partition @var{list} after each element for which @var{pred} returns non-nil.
+
+This function's anaphoric counterpart is @code{--partition-after-pred}.
 
 @example
 @group

dev/examples.el

@@ -807,8 +807,24 @@ value rather than consuming a list to produce a single value."
     (-partition-after-pred #'booleanp '(0 0 t t 0 t)) => '((0 0 t) (t) (0 t))
     (-partition-after-pred #'booleanp '(t)) => '((t))
     (-partition-after-pred #'booleanp '(0 t)) => '((0 t))
-    (--partition-after-pred (= 1 (% it 2)) '(0 0 0 1 0 1 1 0 1))
-    => '((0 0 0 1) (0 1) (1) (0 1)))
+    (--partition-after-pred (= (% it 2) 0) '()) => '()
+    (--partition-after-pred (= (% it 2) 1) '()) => '()
+    (--partition-after-pred (= (% it 2) 0) '(0)) => '((0))
+    (--partition-after-pred (= (% it 2) 1) '(0)) => '((0))
+    (--partition-after-pred (= (% it 2) 0) '(0 1)) => '((0) (1))
+    (--partition-after-pred (= (% it 2) 1) '(0 1)) => '((0 1))
+    (--partition-after-pred (= (% it 2) 0) '(0 1 2)) => '((0) (1 2))
+    (--partition-after-pred (= (% it 2) 1) '(0 1 2)) => '((0 1) (2))
+    (--partition-after-pred (= (% it 2) 0) '(0 1 2 3)) => '((0) (1 2) (3))
+    (--partition-after-pred (= (% it 2) 1) '(0 1 2 3)) => '((0 1) (2 3))
+    (--partition-after-pred t '()) => ()
+    (--partition-after-pred t '(0)) => '((0))
+    (--partition-after-pred t '(0 1)) => '((0) (1))
+    (--partition-after-pred t '(0 1 2)) => '((0) (1) (2))
+    (--partition-after-pred nil '()) => '()
+    (--partition-after-pred nil '(0)) => '((0))
+    (--partition-after-pred nil '(0 1)) => '((0 1))
+    (--partition-after-pred nil '(0 1 2)) => '((0 1 2)))
 
   (defexamples -partition-before-pred
     (-partition-before-pred #'booleanp '()) => '()