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From: Sergio Antoy <antoy_at_cs.pdx.edu>

Date: Thu, 16 Dec 2010 11:45:10 -0800

All right. I think I am getting it, and it is an interesting and

elegant idea. Can the following be a less contrived example?

Suppose a robot moves in an integer plane stepping 1 unit along

either axis direction, but is not allowed to step on the origin.

Could you define a move as

move (x,y) = (x-1,y)

? (x+1,y)

? (x,y-1)

? (x,y+1)

? anti (0,0)

This could be better than some other coding alternatives, except

maybe the constrained constructor pattern.

However, there may be a drawback from an implementation

standpoint. Evaluating choices is already expensive. With the

new meaning, it would become even more expensive.

With the traditional meaning, any solution, say s, of x in x?y can

be immediately used, e.g., output. With the new meaning, before

using s, one should compute all the solution of x and y, to make

sure that an anti s is not found.

Sergio

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Received on Fr Dez 17 2010 - 11:10:17 CET

Date: Thu, 16 Dec 2010 11:45:10 -0800

All right. I think I am getting it, and it is an interesting and

elegant idea. Can the following be a less contrived example?

Suppose a robot moves in an integer plane stepping 1 unit along

either axis direction, but is not allowed to step on the origin.

Could you define a move as

move (x,y) = (x-1,y)

? (x+1,y)

? (x,y-1)

? (x,y+1)

? anti (0,0)

This could be better than some other coding alternatives, except

maybe the constrained constructor pattern.

However, there may be a drawback from an implementation

standpoint. Evaluating choices is already expensive. With the

new meaning, it would become even more expensive.

With the traditional meaning, any solution, say s, of x in x?y can

be immediately used, e.g., output. With the new meaning, before

using s, one should compute all the solution of x and y, to make

sure that an anti s is not found.

Sergio

_______________________________________________

curry mailing list

curry_at_lists.RWTH-Aachen.DE

http://MailMan.RWTH-Aachen.DE/mailman/listinfo/curry

Received on Fr Dez 17 2010 - 11:10:17 CET

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