cs343 p. 63

Rewriting Equations

Given an equation (= ?X (+ ?Y ?Z)), where each of ?X, ?Y, and ?Z could be any expression, we could use the laws of algebra to rewrite the equation as:

(= (- ?X ?Y) ?Z)
(= (- ?X ?Z) ?Y)

Assuming that the variables ?X, ?Y, and ?Z have values, we could create the first pattern using LIST:


(LIST '= (LIST '- ?X ?Y) ?Z)

or using backquote:

`(= (- ,?X ,?Y) ,?Z)

Backquote produces the same code as above; it quotes everything unless an item is un-quoted with a comma.

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