diff options
author | Colin Okay <okay@toyful.space> | 2022-07-28 22:23:20 -0500 |
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committer | Colin Okay <okay@toyful.space> | 2022-07-28 22:23:20 -0500 |
commit | 54b626cd2934aa01d12f6a26a2d30dc026bb06e3 (patch) | |
tree | 1d1eb1e188e26ac91927bf4e8074dd0b2164ca5d /examples | |
parent | 36c004c17f6d7380ab10e3c88983788d85434de4 (diff) |
[example] adde note about dropping ghouls while iterating over them
Diffstat (limited to 'examples')
-rw-r--r-- | examples/09-ghoulspree.lisp | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/examples/09-ghoulspree.lisp b/examples/09-ghoulspree.lisp index 03552f0..a11e6a6 100644 --- a/examples/09-ghoulspree.lisp +++ b/examples/09-ghoulspree.lisp @@ -102,7 +102,14 @@ on which boundary VAL is outside of." when gravity do (apply-gravity-to ghoul accelleration) when (out-of-bounds-p ghoul) - do (ww:drop-unit ghoul))))) + ;; note, it is generally a BadIdeaâ„¢ to delete + ;; something from an array that you are iterating + ;; over. It only works as expected here b/c of + ;; implicit knowledge about the imlementation of the + ;; scene container. A safer way in most cases would be + ;; to `collect ghoul into drop-list` and then deleted + ;; all the collected ghouls in a `finally` clause. + do (ww:drop-unit ghoul))))) (defun random-sign () (if (zerop (random 2)) -1 1)) |