Ignore `back', `fwd', `up', `down', `mark', and `lineup'.

1 files changed, 16 insertions, 0 deletions

diff --git a/eqn.7 b/eqn.7
index 48625e74..346f7480 100644
--- a/eqn.7
+++ b/eqn.7
@@ -203,6 +203,22 @@ In mandoc, this is interpreted as a comment.
 In troff, The circumflex and tilde white-space symbols map to
 fixed-width spaces.
 In mandoc, these characters are synonyms for the space character.
+.It
+The troff implementation of
+.Nm
+allows for equation alignment with the
+.Cm mark
+and
+.Cm lineup
+tokens.
+mandoc discards these tokens.
+The
+.Cm back Ar n ,
+.Cm fwd Ar n ,
+.Cm up Ar n ,
+and
+.Cm down Ar n
+commands are also ignored.
 .El
 .Sh SEE ALSO
 .Xr mandoc 1 ,