The pattern matcher in the file patm.lsp has additional features that are needed for transformations:

• Constant folding and partial evaluation. When certain functions have constant arguments, the functions are evaluated as part of the transformation process. Note: such evaluation must not cause an error; functions that have side-effects (e.g. printing) should not be evaluated.

• Recursion and repetition. Parts of a complex expression must be recursively transformed. Sometimes one transformation will expose an opportunity for constant folding or other transformations.

  ( (+ ?n (+ ?m ?x)) (+ (+ ?n ?m) ?x) )
  where ?m and ?n are numbers, will cause the input (+ 3 (+ 7 foo)) to be transformed to (+ (+ 3 7) foo) and then, by constant folding, to (+ 10 foo) .

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