scala - Invoking curried function -
below implementation of curried function :
scala> def multiply(x: int, y: int) = x * y multiply: (x: int, y: int)int scala> def multiplycurried = (multiply _).curried multiplycurried: int => (int => int) when attempt implement multiplycurried receive exception :
<console>:10: error: missing parameter type multiplycurried(a => b => * b) what correct implementation invoke multiplycurried ?
from wikipedia: currying technique of translating evaluation of function takes multiple arguments (or tuple of arguments) evaluating sequence of functions, each single argument (partial application)
def multiply(x: int, y: int) = x * y //> multiply: (x: int, y: int)int def multiplycurried = (multiply _).curried //> multiplycurried: => int => (int => int) def multiplycurried2(x: int)(y: int) = x * y //> multiplycurried2: (x: int)(y: int)int def multiplycurried3(x:int) = (y:int) => x * y //> multiplycurried3: (x: int)int => int def multiplycurried4 = multiplycurried2 _ //> multiplycurried4: => int => (int => int) multiply(1, 2) //> res1: int = 2 multiplycurried(1)(2) //> res2: int = 2 multiplycurried2(1)(2) //> res3: int = 2 multiplycurried3(1)(2) //> res4: int = 2 multiplycurried2 syntactic sugar multiplycurried3.
as victor correctly points out in comments, multiplycurried , multiplycurried2 not same. implementation of multiplycurried4 contains recipe turn multiplycurried2 function equal multiplycurried.
what's nice currying partial application:
val m = multiplycurried(1) //> m : int => int = <function1> m(2) //> res5: int = 2 val m2 = multiplycurried2(1)_ //> m : int => int = <function1> m2(2) //> res6: int = 2
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