I'd like to know the earliest reference to the Z-combinator. This could be either where the name was first coined, or even the first discussion of a need for an applicative-order Y combinator. I didn't find anything in Barendregt, which was my obvious place to look, nor did I see it in Curry's Combinatory Logic books.

Can someone point me the right direction?

  • 1
    $\begingroup$ The paper History of Lambda-calculus and Combinatory Logic may provide some useful background. It states that the Y combinator first appeared in Rosenbloom's Elements of Mathematical Logic of 1950, following Turing's introduction of a fixed-point combinator. It became know as Curry's Y. $\endgroup$
    – nwr
    Jan 25, 2019 at 4:27


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