One line Scala function to invert (Int => Boolean) function -

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question

if there way in scala define inv function below in 1 line?

// function invert decision function such even/odd/positive/... def inv(f: int => boolean):(int => boolean) = {     def g(a:int):boolean = {         !f(a)     }     g }  // test def even(x:int):boolean = (x % 2 == 0) val odd = inv(even) println("odd(99) %s".format(odd(99))) ---- odd(99) true

problem

tried below !f or !f(a) below got errors. not sure wrong. if explanation can provided, appreciated.

def inv(f: int => boolean):(int => boolean) = !f ---- error: value unary_! not member of int => boolean  def inv(f: a:int => b:boolean):(int => boolean) = !f(a) ---- error: ')' expected ':' found.                                                                                                                                                def inv(f: a:int => b:boolean):(int => boolean) = !f(a)                  ^

you can write 

def inv(f: int => boolean):(int => boolean) = => !f(a)

what's wrong !f: f isn't boolean.

what's wrong def inv(f: a:int => b:boolean): when parser looks @ definition, knows f: going followed type. a can type, can't followed : in case (a:int => b:boolean not type).


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