CODEWITHSUNDEEP
scalainfix-notation
dublintech
dublintech

Reputation: 17785

Brackets needed when using infix approach?

Really simple Scala question.

How come the infix approach to 1 + 2 does not need brackets?

scala>1 + 2
res7: Int = 3

But the dot approach does?

scala>1 .+(2)
res8: Int = 3

scala> 1 .+2
<console>:1: error: ';' expected but integer literal found.
   1 .+2
       ^

Upvotes: 1

Views: 160

Answers (2)

pablisco
pablisco

Reputation: 14237

I think it's to do with language definition:

A left-associative binary operation e1 op e2 is interpreted as e1.op(e2).

http://www.scala-lang.org/docu/files/ScalaReference.pdf

The form 1 .+ 2 is not specified anywhere so my guess is that the compiler is looking for either 1 + 2 or 1.+(2). In fact the compiler converts 1+2 into 1.+(2) normally. When using the . it expects a function and not the infix syntax.

Bottom line: you can use either but not something half way there.

PD: someone commented that calling a method you need to use it like this: obj.somemethod(someparam,foo,bar) but on that case you can also do this: obj somemethod (someparam,foo,bar) and you have to leave the spaces for it to work.

Upvotes: 2

ghik
ghik

Reputation: 10764

Everything in Scala is an object so 1 .+(2) means to call method + on object 1 with parameter 2. And of course if you call a method like this, you need to enclose parameters in brackets, just like in regular obj.somemethod(someparam,foo,bar).

Infix notation (1 + 2) actually means the same thing (it is syntactic sugar to call method with one parameter).

And the space before dot is needed so that dot is interpreted as method invocation and not as decimal separator. Otherwise 1.+(2) or 1.+2 will be interpreted as 1.0 + 2.

Upvotes: 3

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