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 ?
In Scala 2.9 and before, 2. is interpreted as 2.0 so the ambiguous dot denotes a float literal. You’d explicitly call the method by using the syntax (2).+(2).
The ambiguous floating point syntax will however be deprecated in 2.10:
scala> 2.+(2) <console>:1: warning: This lexical syntax is deprecated. From scala 2.11, a dot will only be considered part of a number if it is immediately followed by a digit. 2.+(2) ^ <console>:2: warning: This lexical syntax is deprecated. From scala 2.11, a dot will only be considered part of a number if it is immediately followed by a digit. 2.+(2) ^ <console>:8: warning: This lexical syntax is deprecated. From scala 2.11, a dot will only be considered part of a number if it is immediately followed by a digit. 2.+(2) ^ res1: Double = 4.0 
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 