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The name Y combinator is many decades old, while this graphical notation is not even one decade old. But you do raise an interesting question: How did the fixe
by tromp 5y ago
The name Y combinator is many decades old, while this graphical notation is not even one decade old.
But you do raise an interesting question:
How did the fixed point combinator come to be known as the Y combinator?
- amelius 5y agoProbably just drawing letters from the alphabet. It's like the question: why do we use "x" to denote the unknown value in mathematics, most of the time?
- bidirectional 5y agoThe drawing random letters is true for the lambda in lambda-calculus, but not true for (at least some) combinators. e.g. the K combinator derives from Konstanzfunktion, and I from Identitätsfunktion[1]. So I do think it is an interesting question why Y, and we can't just assume it's arbitrary. [1] https://www.johndcook.com/blog/2014/02/06/schonfinkel-combinators/ https://www.johndcook.com/blog/2014/02/06/schonfinkel-combin...
- amelius 5y agoThen perhaps this reply comes closest to the truth: > Y because the letter Y has one stem which splits in two, just like what the function does. That’s probably the reason, or at least that’s how I look at it.
- amw-zero 5y agoWhy was lambda chosen as the abstraction character in the lambda calculus? Mathematicians just pick random letters and symbols for things.
- yesenadam 5y agoOn the origin of the lambda symbol: https://en.wikipedia.org/wiki/Lambda_calculus#Origin_of_the_lambda_symbol https://en.wikipedia.org/wiki/Lambda_calculus#Origin_of_the_...