Clarified per rms request.

1 files changed, 20 insertions, 25 deletions

diff --git a/etc/ETAGS.EBNF b/etc/ETAGS.EBNF
index 58a9e5196c6..f9bd0bbcf52 100644
--- a/etc/ETAGS.EBNF
+++ b/etc/ETAGS.EBNF
@@ -3,10 +3,10 @@
 This file contains two sections:
 
 1) An EBNF (Extended Backus Normal Form) description of the format of
-   the tags file created by etags.c and interpreted by etags.el
-2) A discussion of tag names and implicit tag names
+    the tags file created by etags.c and interpreted by etags.el;
+2) A discussion of tag names and implicit tag names.
 
-======================= EBNF tag file description =======================
+====================== 1) EBNF tag file description =====================
 
 Productions created from current behavior to aid extensions
 Francesco Potorti` <pot@gnu.org> 2002
@@ -58,14 +58,14 @@ realposition ::= "," unsint | unsint "," | unsint "," unsint
 
 
 
-======================== discussion of tag names =========================
+======================= 2) discussion of tag names =======================
 
-- What are tag names
+- WHAT ARE TAG NAMES
 Tag lines in a tags file are usually made from the above defined pattern
 and by an optional tag name.  The pattern is a string that is searched
 in the source file to find the tagged line.
 
-- Why tag names are good
+- WHY TAG NAMES ARE GOOD
 When a user looks for a tag, Emacs first compares the tag with the tag
 names contained in the tags file.  If no match is found, Emacs compares
 the tag with the patterns.  The tag name is then the preferred way to
@@ -73,23 +73,18 @@ look for tags in the tags file, because when the tag name is present
 Emacs can find a tag faster and more accurately.  These tag names are
 part of tag lines in the tags file, so we call them "explicit".
 
-- Why implicit tag names are even better
+- WHY IMPLICIT TAG NAMES ARE EVEN BETTER
 When a tag line has no name, but a name can be deduced from the pattern,
-we say that the tag line has an implicit tag name.  etags.c uses
-implicit tag names when possible, in order to reduce the number of
-explicit tag names in a tags file, thus reducing the size of the tags
-file.  When the user looks for a tag, and Emacs founds no explicit tag
-names that match it, Emacs then tries to match the tag with an implicit
-tag name.  Such a match occurs when the tag matches a pattern, subject
-to the satisfaction of all the following four rules:
-
- NONAM=" \f\t\n\r()=,;";
-  1. the tag does not contain any of the characters in NONAM;
-  2. the pattern contains the tag as either a rightmost, or rightmost
-     but one character, substring;
-  3. the character, if any, immediately before the tag in the pattern
-     must be a character in NONAM;
-  4. the character, if any, immediately after the tag in the pattern
-     must also be a character in NONAM.
-
-===================== end of discussion on tag names =====================
+we say that the tag line has an implicit tag name.  Often tag names are
+redundant; this happens when the name of a tag is an easily guessable
+substring of the tag pattern.  We define a set of rules to decide
+whether it is possible to deduce the tag name from the pattern, and make
+an unnamed tag in those cases.  The name deduced from the pattern of an
+unnamed tag is the implicit name of that tag.  etags.c uses implicit tag
+names when possible, in order to reduce the size of the tags file.
+  An implicit tag name is deduced from the pattern by discarding the
+last character if it is one of ` \f\t\n\r()=,;', then taking all the
+rightmost consecutive characters in the pattern which are not one of
+those.
+
+===================== end of discussion of tag names =====================