ftp.nice.ch/pub/next/developer/objc/appkit/Crossword.1.1.NIHS.bs.tar.gz#/Crossword.1.1.NIHS.bs/Source/BackjumpSquare.m

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/*

File BackjumpSquare.m

These are the squares used for backjumping search.  When a letter has no remaining possibilities, the words that intersect at that letter are added to the current nogood.  The current nogood is cleared whenever a letter is successfully filled.

*/

#import <appkit/appkit.h>

#import "Backjump.h"
#import "Puzzle.h"


/* ÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐ  */


#define position(i)		((wordPosition *) [words  elementAt: i])


/* ÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐ  */


@implementation BackjumpSquare


- startOver
{
	id		state;
	
	if ([state = [puzzle  getState]  inNogood]) [state  isok];
	return self;
}


- erase
{
	[self  chooseLetter];
	[[[self  clear]  setLetter: WILDCARD]  show];
	
	return self;
}


- clear
{
	id		state;
	int		i;
	
	if (!injump)
	{
		state = [puzzle  getState];
		i = [words  count];
		while (i--) [state  mustChange: position(i)->word];
	}
	
	return [super  clear];
}


- setLetter: (char) theLetter
{
	[super  setLetter: theLetter];
	if (letter != WILDCARD) [[puzzle  getState]  isok];
			
	return self;
}


- (char) chooseLetter
{
	char	best;
	int		i;
	
	if (![[puzzle  getState]  inNogood]) injump = NO;
	else
	{
		injump = YES;
		i = [words  count];
		while (i--) injump &= ![position(i)->word  mustChange];
	}
		
	if (!injump) best = [super  chooseLetter];
	else best = WILDCARD;
	
	if (injump)
			[self  setStatus: JUMPED];		else
			[self  clearStatus: JUMPED];
	
	return best;
}


@end

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