Comment by needlesslygrim
1 year ago
Well, ML (or at least the first versions of it) used a λx • x syntax [1] for λ-abstractions, the same (excluding the use of • over .) notation as used with the Lambda Calculus, and I've always assumed \ was an ASCII stand in.
[1]: https://homepages.inf.ed.ac.uk/wadler/papers/papers-we-love/... (can be spotted on page 353)
That paper isn't showing real ML syntax itself; it's a mathematical presentation to demonstrate how the type system algorithm works. The actual original LCF/ML syntax would differ. I don't believe it used an actual lambda character, although for the life of me I can't find any evidence one way or another, not even in the LCF source code (https://github.com/theoremprover-museum/LCF77)
But yes, the slash is just an ASCII stand-in for a lambda.
ETA: I tracked down a copy of the Edinburgh LCF text and I have to eat crow. It doesn't use a lambda, but it does use a slash rather than a reserved word. The syntax, per page 22, is in fact, `\x. e`. Similar to Haskell's, but with a dot instead of an arrow.
https://archive.org/details/edinburghlcfmech0000gord
Well if you're going to eat crow, I may as well eat pigeon, for I didn't realise that paper wasn't showing real source.
Thanks for the link to the LCF text though :^)