Call-by-need, neededness and all that

01/31/2018

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by   Delia Kesner, et al.

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We show that call-by-need is observationally equivalent to weak-head needed reduction. The proof of this result uses a semantical argument based on a (non-idempotent) intersection type system called V. Interestingly, system V also allows to syntactically identify all the weak-head needed redexes of a term.