 # Currying vs Partially Applied Function

In this blog, I’m going to discuss about currying and partially applied functions.

###### CURRYING

Currying splits method with multiple parameters into a chain of functions – each with one parameter.

Let’s understand currying using an example:

`scala> def multiply(a: Int)(b: Int)(c: Int) = a * b * c`

is the same as:

`def multiply(a: Int) = (b: Int) => (c: Int) => a * b * c`

multiply is a curried function that takes three parameters a, b and c.
Invoke multiply function as:

```multiply(1)(_)
res9: Int => (Int => Int) = \$\$Lambda\$1118/1682999176@30b1c5d5```

will result in another function that takes interger as an input and yields a lambda expression (Int => Int).

```scala> res9(2)(_)
res10: Int => Int = \$\$Lambda\$1119/2012237082@27682fa9```

will result in another function that takes interger as an input and returns integer as result.

```scala> res10(3)
res11: Int = 6```

res11 is the final result.

###### PARTIALLY APPLIED FUNCTIONS

Pass to function less arguments than it has in its declaration. Scala returns a new function with rest of arguments that need to be passed.

```def isInRange(leftBound: Int, num: Int, rightBound: Int): Boolean = {
if (leftBound < num && num < rightBound) true
else false
}
isInRange(_: Int, 5, _: Int)
will return another function that will take two integers as an argument and result type will be of type Boolean (Int, Int) => Boolean.</p>
scala> isInRange(0, 8)
res0: Boolean = true
scala>(isInRange _).curried
res28: Int => (Int => (Int => Boolean)) = scala.Function3\$\$Lambda\$1322/926382023@3e9cceff```

will split the isInRange method into a chain of functions each with one parameter.

###### DIFFERENCE BETWEEN CURRYING AND PARTIALLY APPLIED FUNCTION

PARTIALLY APPLIED FUNCTION EXAMPLE

```scala> def isDivisible(numberOne: Int, numberTwo: Int) = ((numberOne % numberTwo) == 0)
isDivisible: (numberOne: Int, numberTwo: Int)Boolean

scala> isDivisible _
res23: (Int, Int) => Boolean = \$\$Lambda\$1285/1740173358@6fdc624```

partially applying a normal function(isDivisible) results in a function(res21) that takes all parameters [ (Int, Int) => Boolean ].

```scala> res23(4)
res26: Int => Boolean = scala.Function2\$\$Lambda\$1320/451962020@40c78bd1

scala> res26(2)
res27:Boolean = true```

will give true result.

CURRYING EXAMPLE

```scala> def isDivisibleCurried(numberOne: Int)(numberTwo: Int) = ((numberOne % numberTwo) == 0)
isDivisibleCurried: (numberOne: Int)(numberTwo: Int)Boolean

scala> isDivisibleCurried _
res22: Int => (Int => Boolean) = \$\$Lambda\$1298/27138712@4ec8083```

partially applying a function on isDivisibleCurried will create a chain of functions, one per parameter list [ Int => (Int => Boolean) ].  