Higher Order Wat

gistfile1.scala

def add(x: Int, y: Int = 1): Int = x + y
 
def transform(z: Int, transformer: (Int, Int) => Int): Int = transformer(z)
 
// Exiting paste mode, now interpreting.
 
<console>:9: error: not enough arguments for method apply: (v1: Int, v2: Int)Int in trait Function2.
Unspecified value parameter v2.
       def transform(z: Int, transformer: (Int, Int) => Int): Int = transformer(z)

gistfile2.scala

scala> def add(x: Int = 1, y: Int = 2): Int = x + y
add: (x: Int, y: Int)Int

scala> add()
res0: Int = 3


scala> def transform(z: Int, transformer: (Int, Int) => Int): Int = transformer()
<console>:7: error: not enough arguments for method apply: (v1: Int, v2: Int)Int in trait Function2.
Unspecified value parameters v1, v2.
       def transform(z: Int, transformer: (Int, Int) => Int): Int = transformer()