inform7/retrospective/6M62/Internal/I6T/Char.i6t

B/chart: Char Template.
 
@Purpose: To decide whether letters are upper or lower case, and convert
between the two.
 
@-------------------------------------------------------------------------------

@p Char Is Of Case.
The following decides whether a character |c| belongs to case |case|, where
0 means lower case and 1 means upper. |c| is interpreted according to the
character casing chart in "UnicodeData.i6t", which means, it will be
ZSCII for the Z-machine and Unicode for Glulx.

@c
[ CharIsOfCase c case
	i tab min max len par;
	if (c<'A') rfalse;
	if (case == 0) {
		if ((c >= 'a') && (c <= 'z')) rtrue;
		tab = CharCasingChart0;
	} else {
		if ((c >= 'A') && (c <= 'Z')) rtrue;
		tab = CharCasingChart1;
	}
	if (c<128) rfalse;
	while (tab-->i) {
		min = tab-->i; i++;
		len = tab-->i; i++;
		i++;
		par = 0;
		if (len<0) { par = 1; len = -len; }
		if (c < min) rfalse;
		if (c < min+len) {
			if (par) { if ((c-min) % 2 == 0) rtrue; }
			else { rtrue; }
		}
	}
	rfalse;
];

@p Char To Case.
And the following converts character |c| to the desired case, or returns
it unchanged if it is not a letter with variant casings.

@c
[ CharToCase c case
	i tab min max len par del f;
	if (c<'A') return c;
	if (case == 1) {
		if ((c >= 'a') && (c <= 'z')) return c-32;
		tab = CharCasingChart0;
	} else {
		if ((c >= 'A') && (c <= 'Z')) return c+32;
		tab = CharCasingChart1;
	}
	if (c<128) return c;
	while (tab-->i) {
		min = tab-->i; i++;
		len = tab-->i; i++;
		del = tab-->i; i++;
		par = 0;
		if (len<0) { par = 1; len = -len; }
		if (c < min) return c;
		if (c < min+len) {
			f = false;
			if (par) { if ((c-min) % 2 == 0) f = true; }
			else { f = true; }
			if (f) {
				if (del == UNIC_NCT) return c;
				return c+del;
			}
		}
	}
	return c;
];

@p Reversing Case.
It's convenient to provide this relatively fast routine to reverse the
case of a letter since this is an operation used frequently in regular
expression matching (see "RegExp.i6t").

@c
#IFDEF TARGET_ZCODE;
[ TEXT_TY_RevCase ch;
	if (ch<'A') return ch;
	if ((ch >= 'a') && (ch <= 'z')) return ch-'a'+'A';
	if ((ch >= 'A') && (ch <= 'Z')) return ch-'A'+'a';
	if (ch<128) return ch;
	if ((ch >= 155) && (ch <= 157)) return ch+3; ! a, o, u umlaut in ZSCII
	if ((ch >= 158) && (ch <= 160)) return ch-3; ! A, O, U umlaut
	if ((ch >= 164) && (ch <= 165)) return ch+3; ! e, i umlaut
	if ((ch >= 167) && (ch <= 168)) return ch-3; ! E, I umlaut
	if ((ch >= 169) && (ch <= 174)) return ch+6; ! a, e, i, o, u, y acute
	if ((ch >= 175) && (ch <= 180)) return ch-6; ! A, E, I, O, U, Y acute
	if ((ch >= 181) && (ch <= 185)) return ch+5; ! a, e, i, o, u grave
	if ((ch >= 186) && (ch <= 190)) return ch-5; ! A, E, I, O, U grave
	if ((ch >= 191) && (ch <= 195)) return ch+5; ! a, e, i, o, u circumflex
	if ((ch >= 196) && (ch <= 200)) return ch-5; ! A, E, I, O, U circumflex
	if (ch == 201) return 202; ! a circle
	if (ch == 202) return 201; ! A circle
	if (ch == 203) return 204; ! o slash
	if (ch == 204) return 203; ! O slash
	if ((ch >= 205) && (ch <= 207)) return ch+3; ! a, n, o tilde
	if ((ch >= 208) && (ch <= 210)) return ch-3; ! A, N, O tilde
	if (ch == 211) return 212; ! ae ligature
	if (ch == 212) return 211; ! AE ligature
	if (ch == 213) return 214; ! c cedilla
	if (ch == 214) return 213; ! C cedilla
	if (ch == 215 or 216) return ch+2; ! thorn, eth
	if (ch == 217 or 218) return ch-2; ! Thorn, Eth
	if (ch == 220) return 221; ! oe ligature
	if (ch == 221) return 220; ! OE ligature
	return ch;
];
#IFNOT;
[ TEXT_TY_RevCase ch;
	if (ch<'A') return ch;
	if ((ch >= 'a') && (ch <= 'z')) return ch-'a'+'A';
	if ((ch >= 'A') && (ch <= 'Z')) return ch-'A'+'a';
	if (ch<128) return ch;
	if (CharIsOfCase(ch, 0)) return CharToCase(ch, 1);
	if (CharIsOfCase(ch, 1)) return CharToCase(ch, 0);
	return ch;
];
#ENDIF;

@p Testing.
Not actually used: simply for testing the tables.

@c
[ CharTestCases case i j;
	for (i=32: i<$E0; i++) {
		if ((i>=127) && (i<155)) continue;
		print i, " - ", (char) i, " -";
		if (CharIsOfCase(i, 0)) print "  lower";
		if (CharIsOfCase(i, 1)) print "  upper";
		j = CharToCase(i, 0); if (j ~= i) print "  tolower: ", (char) j;
		j = CharToCase(i, 1); if (j ~= i) print "  toupper: ", (char) j;
		print "^";
	}
];