# What is the Haskell-style type signature called (i.e., who is it named after)?

A type signature in Haskell is written in the following format:

functionName :: arg1Type -> arg2Type -> returnType


There's a (hyphenated, after a person or persons) name for this style of type signature (which predates Haskell), but it's escaping me and I can't find it anywhere.

• This style of definition isn't really due to Haskell is it? It's existed in type theory (70s and earlier) which led to languages inspiring Haskell and far before that it existed in the mathematical community at large. – jozefg Jan 6 '16 at 19:19
• Yes, correct -- it's not exclusive to Haskell. I'll make this clear. – Jake Romer Jan 6 '16 at 19:20
• I'd look into the origins of ML Syntax, I think it likely originates from there (though it's possible it can be traced earlier back). – jmite Jan 6 '16 at 23:17
• By the way: in Haskell, and in several other FP languages, it's more common to find curried functions/signatures f :: arg1Type -> arg2Type -> returnType instead. – chi Jan 7 '16 at 19:07
• Do you mean Church-style (as opposed to Curry-style) for lambda calculus, i.e. type checking only instead of type inference? – Cactus Jan 8 '16 at 6:04