docs: clarify the coverage-exclude and token-seed comments

The Makefile's `COVERAGE_EXCLUDE' comment said why `test-all-comp-errors.el' is excluded but not why `test-lorem-optimum-benchmark.el' is. It now notes that undercover's instrumentation slows execution enough to fail the benchmark's wall-clock assertions. And `cj/markov-generate' now has a comment explaining why `tokens' is seeded reversed (`(list w2 w1)'): the list is built with `push' and `nreverse'd at the end, so without the note the reversed seed reads like a bug at a glance.

2 files changed, 5 insertions, 2 deletions

diff --git a/Makefile b/Makefile
index 5e35a4cc..3b5d9024 100644
--- a/Makefile
+++ b/Makefile
@@ -228,8 +228,9 @@ COVERAGE_DIR = .coverage
 COVERAGE_FILE = $(COVERAGE_DIR)/simplecov.json
 
 # Test files that can't coexist with undercover's instrumentation
-# (e.g. test-all-comp-errors byte-compiles modules, which fails on
-# instrumented sources).  Excluded from `make coverage' only.
+# (test-all-comp-errors byte-compiles modules, which fails on instrumented
+# sources; test-lorem-optimum-benchmark's wall-clock assertions fail when
+# instrumentation slows execution).  Excluded from `make coverage' only.
 COVERAGE_EXCLUDE = \
 	$(TEST_DIR)/test-all-comp-errors.el \
 	$(TEST_DIR)/test-lorem-optimum-benchmark.el
diff --git a/modules/lorem-optimum.el b/modules/lorem-optimum.el
index 7b19125e..a6bec657 100644
--- a/modules/lorem-optimum.el
+++ b/modules/lorem-optimum.el
@@ -142,6 +142,8 @@ Uses O(n) algorithm by matching at position instead of creating substrings."
 					  (cj/markov-random-key chain)))
 		   (w1 (car state))
 		   (w2 (cadr state))
+		   ;; tokens is built with `push' (prepend) and `nreverse'd at the end,
+		   ;; so seed it reversed -- w2 then w1 -- to get w1 w2 ... after the flip.
 		   (tokens (list w2 w1)))
 	  (dotimes (_ (max 0 (- n 2)))
 		(let ((next (cj/markov-next-word chain state)))