* fns.c (Fcompare_strings): Doc fix.

* strings.texi (Text Comparison): Doc fix for compare-strings.

Fixes: debbugs:13081

4 files changed, 39 insertions, 21 deletions

diff --git a/doc/lispref/ChangeLog b/doc/lispref/ChangeLog
index 9dbce599bd1..9aeff403ec3 100644
--- a/doc/lispref/ChangeLog
+++ b/doc/lispref/ChangeLog
@@ -1,3 +1,7 @@
+2012-12-15  Chong Yidong  <cyd@gnu.org>
+
+        * strings.texi (Text Comparison): Doc fix for compare-strings.
+
 2012-12-09  Stefan Monnier  <monnier@iro.umontreal.ca>
 
         * control.texi (Pattern matching case statement): New node.
diff --git a/doc/lispref/strings.texi b/doc/lispref/strings.texi
index 865435c91b3..c127cec8f8a 100644
--- a/doc/lispref/strings.texi
+++ b/doc/lispref/strings.texi
@@ -517,25 +517,29 @@ comparison ignores case differences.
 @end defun
 
 @defun compare-strings string1 start1 end1 string2 start2 end2 &optional ignore-case
-This function compares the specified part of @var{string1} with the
+This function compares a specified part of @var{string1} with a
 specified part of @var{string2}.  The specified part of @var{string1}
-runs from index @var{start1} up to index @var{end1} (@code{nil} means
-the end of the string).  The specified part of @var{string2} runs from
-index @var{start2} up to index @var{end2} (@code{nil} means the end of
-the string).
-
-The strings are both converted to multibyte for the comparison
-(@pxref{Text Representations}) so that a unibyte string and its
-conversion to multibyte are always regarded as equal.  If
-@var{ignore-case} is non-@code{nil}, then case is ignored, so that
-upper case letters can be equal to lower case letters.
+runs from index @var{start1} (inclusive) up to index @var{end1}
+(exclusive); @code{nil} for @var{start1} means the start of the
+string, while @code{nil} for @var{end1} means the length of the
+string.  Likewise, the specified part of @var{string2} runs from index
+@var{start2} up to index @var{end2}.
+
+The strings are compared by the numeric values of their characters.
+For instance, @var{str1} is considered ``smaller than'' @var{str2} if
+its first differing character has a smaller numeric value.  If
+@var{ignore-case} is non-@code{nil}, characters are converted to
+lower-case before comparing them.  Unibyte strings are converted to
+multibyte for comparison (@pxref{Text Representations}), so that a
+unibyte string and its conversion to multibyte are always regarded as
+equal.
 
 If the specified portions of the two strings match, the value is
 @code{t}.  Otherwise, the value is an integer which indicates how many
-leading characters agree, and which string is less.  Its absolute value
-is one plus the number of characters that agree at the beginning of the
-two strings.  The sign is negative if @var{string1} (or its specified
-portion) is less.
+leading characters agree, and which string is less.  Its absolute
+value is one plus the number of characters that agree at the beginning
+of the two strings.  The sign is negative if @var{string1} (or its
+specified portion) is less.
 @end defun
 
 @defun assoc-string key alist &optional case-fold
diff --git a/src/ChangeLog b/src/ChangeLog
index fe30528da91..c123606efda 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,7 @@
+2012-12-15  Chong Yidong  <cyd@gnu.org>
+
+        * fns.c (Fcompare_strings): Doc fix (Bug#13081).
+
 2012-12-14  Eli Zaretskii  <eliz@gnu.org>
 
         * w32.c (get_name_and_id): Always pass NULL as the first argument
diff --git a/src/fns.c b/src/fns.c
index b1ba5ce9509..539e8888dbc 100644
--- a/src/fns.c
+++ b/src/fns.c
@@ -211,12 +211,18 @@ Symbols are also allowed; their print names are used instead.  */)
 
 DEFUN ("compare-strings", Fcompare_strings, Scompare_strings, 6, 7, 0,
        doc: /* Compare the contents of two strings, converting to multibyte if needed.
-In string STR1, skip the first START1 characters and stop at END1.
-In string STR2, skip the first START2 characters and stop at END2.
-END1 and END2 default to the full lengths of the respective strings.
-
-Case is significant in this comparison if IGNORE-CASE is nil.
-Unibyte strings are converted to multibyte for comparison.
+The arguments START1, END1, START2, and END2, if non-nil, are
+positions specifying which parts of STR1 or STR2 to compare.  In
+string STR1, compare the part between START1 (inclusive) and END1
+\(exclusive).  If START1 is nil, it defaults to 0, the beginning of
+the string; if END1 is nil, it defaults to the length of the string.
+Likewise, in string STR2, compare the part between START2 and END2.
+
+The strings are compared by the numeric values of their characters.
+For instance, STR1 is "less than" STR2 if its first differing
+character has a smaller numeric value.  If IGNORE-CASE is non-nil,
+characters are converted to lower-case before comparing them.  Unibyte
+strings are converted to multibyte for comparison.
 
 The value is t if the strings (or specified portions) match.
 If string STR1 is less, the value is a negative number N;