Question

When I invoke + on 2 I get an Int back, but when its done using explicit method call I get Double instead.

scala> 2+2
res1: Int = 4

scala> 2.+(2)
res2: Double = 4.0

It seems that .+() is invoked on implicit converted Int to Double.

scala> 2.+
<console>:16: error: ambiguous reference to overloaded definition,
both method + in class Double of type (x: Char)Double
and  method + in class Double of type (x: Short)Double
match expected type ?
              2.+
                ^

Why is that so ?

Answer 1

The reason is not in explicit method call — by writing 2.+ you specifying Double on the left side and then calling addition operator on it:

scala> 2.
res0: Double = 2.0