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answer re: Can anyone explain the second reduction rule for ZF-expressions?

Jun 24 '18

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The notation you mention is not Haskell code, but a meta-notation for substitution which is frequently used in programming languages theory.

If e and t are Haskell expressions, and x is a Haskell variable, we write e [x := t] to denote the expression e where all the free occurrences…

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