Omitting Constructor Parentheses

[Seyed H. HAERI (Hossein)]

Dear all,

I have a class

case class Left(val e: Expr = Num(1)) extends Command

which I'd like to use like

val v = Left

in which I'd be omitting the constructor's parentheses -- just like those of any other purely functional method. I get the following error under Scala 2.11.8, however:

type mismatch; found : m1.syntax.Left.type required: m2.syntax.Command

Why is that?

TIA,

--Hossein

 

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[Naftoli Gugenheim]

Because it's the name of the companion object that's generated with the case class. In fact the syntax with parentheses only works by desugaring to a call to the companion's apply method

On Wed, Apr 12, 2017, 7:31 PM Seyed H. HAERI (Hossein) <[hidden email]> wrote:

Dear all,

I have a class

case class Left(val e: Expr = Num(1)) extends Command

which I'd like to use like

val v = Left

in which I'd be omitting the constructor's parentheses -- just like those of any other purely functional method. I get the following error under Scala 2.11.8, however:

type mismatch; found : m1.syntax.Left.type required: m2.syntax.Command

Why is that?

TIA,

--Hossein

 

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