Better documentation for 'lctype.h'
The old documentation said that 'ltolower' only works for alphabetic
characters. However, 'l_str2d' uses it (correctly) also on dots ('.').
diff --git a/lctype.h b/lctype.h
index cbff4d7..864e190 100644
--- a/lctype.h
+++ b/lctype.h
@@ -13,7 +13,7 @@
/*
** WARNING: the functions defined here do not necessarily correspond
** to the similar functions in the standard C ctype.h. They are
-** optimized for the specific needs of Lua
+** optimized for the specific needs of Lua.
*/
#if !defined(LUA_USE_CTYPE)
@@ -61,13 +61,19 @@
#define lisprint(c) testprop(c, MASK(PRINTBIT))
#define lisxdigit(c) testprop(c, MASK(XDIGITBIT))
+
/*
-** this 'ltolower' only works for alphabetic characters
+** In ASCII, this 'ltolower' is correct for alphabetic characters and
+** for '.'. That is enough for Lua needs. ('check_exp' ensures that
+** the character either is an upper-case letter or is unchanged by
+** the transformation, which holds for lower-case letters and '.'.)
*/
-#define ltolower(c) ((c) | ('A' ^ 'a'))
+#define ltolower(c) \
+ check_exp(('A' <= (c) && (c) <= 'Z') || (c) == ((c) | ('A' ^ 'a')), \
+ (c) | ('A' ^ 'a'))
-/* two more entries for 0 and -1 (EOZ) */
+/* one entry for each character and for -1 (EOZ) */
LUAI_DDEC(const lu_byte luai_ctype_[UCHAR_MAX + 2];)
