add three paragraphs from chess-pos.el commentary

1 files changed, 10 insertions, 0 deletions

diff --git a/chess.texi b/chess.texi
index e4e0308..89bc6f2 100644
--- a/chess.texi
+++ b/chess.texi
@@ -121,12 +121,19 @@ Chess puzzles are most often provided as a set of positions.
 
 @subsection Position coordinates
 
+First of all, a coordinate system of octal indices is
+used, where ?\044 signifies rank 4 file 4 (i.e., "e4").  Rank is
+numbered 0 to 7, top to bottom, and file is 0 to 7, left to right.
+
 @c lispfun chess-index-rank
 
 @c lispfun chess-index-file
 
 @c lispfun chess-rf-to-index
 
+For those who wish to use ASCII coordinates, such as "e4", there
+are two conversion functions:
+
 @c lispfun chess-coord-to-index
 
 @c lispfun chess-index-to-coord
@@ -135,6 +142,9 @@ Chess puzzles are most often provided as a set of positions.
 
 @subsection Position details
 
+With an octal index value, you can look up what's on a particular
+square, or set that square's value:
+
 @c lispfun chess-pos-piece
 
 @c lispfun chess-pos-piece-p