Clarify justification for ditching the denominator.

diff --git a/src/runtime/arith.scm b/src/runtime/arith.scm
index 60459c49e23ebb2a818084f65e4f324b19fcd7c9..2eb29f5782b71f4386dd04fbdda1997210378038 100644 (file)
--- a/src/runtime/arith.scm
+++ b/src/runtime/arith.scm
@@ -2232,7 +2232,7 @@ USA.
   (guarantee-real t 'logit-exp)
   (cond ((<= t -37)
          ;; e^t < eps/2, so since log(e^t/(1 - e^t)) = t - log(1 -
-         ;; e^t), we have
+         ;; e^t), and |log(1 - e^t)| < 1 < |t|, we have
          ;;
          ;;     |t - log(e^t/(1 - e^t))|/|log(e^t/(1 - e^t))|
          ;;      = |log(1 - e^t)|/|t - log(1 - e^t)|.