How to unimport String “+” operator in Scala?

问题

I'm writing a DSL where the "+" operator is strictly numeric, like some other popular languages. It's close, but the String "+" operator is messing up my implicit conversions. What's the syntax for unimporting an operator of the String class?

Just to be clearer, instead of this:

scala> var x = "2" + 3;
x: java.lang.String = 23

I'd like to get x: Int = 5

I imagine I just need 2 things to make that happen:

• Remove (unimport within my scope) the definition of "+" from Strings
• Define an implicit conversion of String to Int

I'm stuck on the first step.

Thanks

回答1:

According to section 12.3.1 of the Scala spec, the + method for String has special treatment by the compiler. I don't know for sure, but I think this means you can't "unimport" it, which is a shame because it really breaks the type system (much like the related toString method).

Could you use a different name for the operator in your DSL, eg, ++ or &?

回答2:

The + method for a string is a method on of the String class (and therefore on each string object), and as such it cannot be unimported.

回答3:

You can't unimport it, but you could use +: and define it on the int class. What would be best is if you write it like this: "2".toInt + 3.

来源：https://stackoverflow.com/questions/2664274/how-to-unimport-string-operator-in-scala