added :extra-cleanup keywoard to inflate!

1 files changed, 14 insertions, 3 deletions

diff --git a/gtwiwtg.lisp b/gtwiwtg.lisp
index 35f830d..bb377e1 100644
--- a/gtwiwtg.lisp
+++ b/gtwiwtg.lisp
@@ -409,13 +409,19 @@ Error Condition:
        (stop gen)))))
 
 
-(defun inflate! (fn gen)
+(defun inflate! (fn gen &key extra-cleaup)
   "FN is expected to be a function that accepts elements of GEN and
 returns a new generator.  
 
 The generator (INFLATE! FN GEN) generates each element of an
 intermediate generator (FN X) for each X generated by GEN.
 
+When a thunk is supplied to EXTRA-CLEANUP, then that thunk will be
+called when the inflated generator is stopped. EXTRA-CLEANUP exists
+for the case when FN returns generators that are not being created
+within the body of FN, but are merely being \"looked up\" somehow. See
+the implementation of CONCAT! for an example.
+
 Here is an example:
 
 > (let ((keys (seq '(:name :occupation :hobbies)))
@@ -457,7 +463,8 @@ Error Conditions:
          :clean-up
          (lambda ()
            (stop gen)
-           (when sub-gen (stop sub-gen)))))))
+           (when sub-gen (stop sub-gen))
+           (when extra-cleanup (funcall extra-cleanup)))))))
 
 
 (defun concat! (gen &rest gens)
@@ -469,7 +476,11 @@ Error Conditions:
  - If any of the generators has been used elsewhere, an error will be sigalled.
 "
   (sully-when-clean (list* gen gens))
-  (inflate! #'identity (seq (list* gen gens))))
+  (inflate! #'identity (seq (list* gen gens))
+            ;; in the case that not all arguments are consumed,
+            ;; explicitly stop each one at clean-up time.
+            :extra-cleanup (lambda () 
+                             (dolist (g (list* gen gens)) (stop g)))))
 
 (defun zip! (gen &rest gens)
   "Is a shortcut for (MAP! #'LIST GEN1 GEN2 ...)"