Why in some cases, I cannot use {} when passing arguments

Question

In following definitions, I can use {} instead of () for curried functions but not for regular functions. Why?

//curried
scala> def add(i:Int)(j:Int) = {i+j}
add: (i: Int)(j: Int)Int

scala> add(1)(2)
res19: Int = 3

//{} works
scala> add(1){2}
res20: Int = 3

//{} works again
scala> add{1}{2}
res21: Int = 3

//non curried
scala> def add(i:Int,j:Int) = {i+j}
add: (i: Int, j: Int)Int

//use of {} creates error
scala> add{1,2}
<console>:1: error: ';' expected but ',' found.
add{1,2}
     ^

Relevant: https://stackoverflow.com/questions/4386127/what-is-the-formal-difference-in-scala-between-braces-and-parentheses-and-when — Jean-Philippe Pellet, Sep 20 '17 at 09:02

score 4 · Accepted Answer · answered Sep 20 '17 at 08:35

{} is code block, the last value in code block is the return value of this.

for add(1){2} means the second code block return value 2 as the second parameter
for add{1}{2} means: first code block return 1 as parameter, second code block return 2 as second parameter

so for add{1,2} doesn't have any meaning, this is not a correct syntax.

Why in some cases, I cannot use {} when passing arguments

1 Answers1