Question

Given the functions:

let doTrue = fun(x) -> true
let doFalse = fun(x) -> false

I want to reuse the function signature so that i can get

let myFunDefinition = ??? // <-- this is the function signature that i am trying to reuse
let doTrue = myFunDefinition -> true // <-- now i don't have to type fun(x) any more
let doFalse = myFunDefinition -> false

Is it possible to define for reuse a function signature?

Answer 1

Even after the edits, your question doesn’t really make sense to me. First of all, the signature of doTrue and doFalse is 'a -> bool as you have written them, but I don’t think that this is really relevant to your question because I don’t see what it would mean to “reuse” the signature. Instead, it seems like you want some form of text macro that will allow you to type myFunDefinition and have that replaced by the text fun (x). Aside from the fact that your replacement text is longer than the original text, here are a few thoughts:

• F# doesn’t have text replacement macros, so if that’s the exact feature you want, you’re out of luck.
• If you want to save typing, you could at least use the more concise formulation let doTrue x = ... instead of let doTrue = fun x -> ...

• If you actually want doTrue and doFalse to be the application of some other function to true and false, then that is easy:

  let myFunDefinition b = {{some function of b}}
  let doTrue = myFunDefinition true
  let doFalse = myFunDefinition false
  

  In this case, perhaps this is what you’re looking for:

  let myFunDefinition b _ = b
  ...
  

  (?) This just ignores the second argument (which becomes the first argument of doTrue and doFalse because they partially apply myFunDefinition to the first arguments of true or false, respectively).

• If you instead want some other sort of abstraction, then the other answers make some reasonable guesses as to what that might mean. In general, you will get more helpful answers if you spend more time articulating your question so that it clearly communicates what you are trying to do.