document .Bl -column, and the bug if the first .Bl doesn't have -width

share/man/man7/mdoc.samples.7

@@ -1,4 +1,4 @@
-.\"	$NetBSD: mdoc.samples.7,v 1.11 1997/11/24 06:29:16 lukem Exp $
+.\"	$NetBSD: mdoc.samples.7,v 1.12 1997/11/24 12:43:25 lukem Exp $
 .\"
 .\" Copyright (c) 1990, 1993
 .\"	The Regents of the University of California.  All rights reserved.
@@ -37,7 +37,7 @@
 .\" times and is guaranteed to give a worst case performance
 .\" for an already extremely slow package.
 .\"
-.Dd December 30, 1993
+.Dd November 24, 1997
 .Os
 .Dt MDOC.SAMPLES 7
 .Sh NAME
@@ -2309,8 +2309,8 @@ each list must end with the
 .Ql ".El"
 macro.
 Lists may be nested within themselves and within displays.
-Columns may be used inside of lists, but lists are unproven
-inside of columns.
+The use of columns inside or lists or lists inside of columns
+is unproven.
 .Pp
 In addition, several list attributes may be specified such as
 the width of a tag, the list offset, and compactness
@@ -2542,6 +2542,35 @@ as if the macro name had been supplied as the width.
 However,
 if another item in the list is given with a different callable
 macro name, a new and nested list is assumed.
+.Pp
+.It Fl column
+This list type generates multiple columns.
+The number of columns and the width of each column is determined by
+the arguments to the
+.Fl column
+list.
+Each
+.Ql ".It"
+argument is parsed to make a row, each column within the
+row is a separate argument separated by a tab or the
+.Ql ".Ta"
+macro.
+.El
+The table:
+.Bl -column "String" "Nroff" "Troff" -offset indent
+.It Sy "String" Ta Sy "Nroff" Ta Sy "Troff"
+.It Li "<=" Ta \&<\&= Ta \*(<=
+.It Li ">=" Ta \&>\&= Ta \*(>=
+.El
+.Pp
+was produced by:
+.Bd -literal -offset indent
+\&.Bl -column "String" "Nroff" "Troff" -offset indent
+\&.It Sy "String" Ta Sy "Nroff" Ta Sy "Troff"
+\&.It Li "<=" Ta \&<\&= Ta \*(<=
+\&.It Li ">=" Ta \&>\&= Ta \*(>=
+\&.El
+.Ed
 .Sh PREDEFINED STRINGS
 The following strings are predefined as may be used by
 preceding with the troff string interpreting sequence
@@ -2807,6 +2836,15 @@ breaks (other than the initial header and footer) when using
 nroff occasionally places an unsightly partially filled line (blank)
 at the would be bottom of the page.
 .Pp
+If the outer-most list definition doesn't have a
+.Fl width
+argument, the
+.Ql ".It"
+elements of inner lists may not work (producing a list where
+each successive element
+.Sq walks
+to the right).
+.Pp
 The list and display macros to not do any keeps
 and certainly should be able to.
 .\" Note what happens if the parameter list overlaps a newline