What does the SQueryL tilde operator do?

Question

I was reading the SQueryL documentation on updating and I saw:

update(songs)(s =>
  where(s.title === "Watermelon Man")
  set(s.title := "The Watermelon Man",
      s.year  := s.year.~ + 1)
)

I had a hard time finding the ~ method from the SQueryL source code and the linked documentation obviously doesn't tell me what it does either. Does anyone care to explain?

The documentation seems incomplete... perhaps try their mailing list? — Rafe Kettler, Dec 18 '10 at 07:30
I've asked the discussion group as the docs are broken and I'm curious. — Channing Walton, Dec 18 '10 at 08:00

score 4 · Accepted Answer · answered Dec 18 '10 at 11:16

I recall reading about the tilde operator not too long ago on the Schema Definition Page. It is about disambiguating between a primitive and a custom type, although (as I am just beginning to learn Scala) it still sounds a bit vague to me ;). To quote a little piece

...

important : in PrimitiveTypes mode there can be ambiguities between numeric operators

When using org.squeryl.PrimitiveTypeMode, the compiler will treat an expression like the one in the next example as a Boolean. The .~ function is needed to tell the compiler that the left side is a node of TypedExpressionNode[Int] which will cause the whole expression to be a LogicalBoolean which is what the where clause takes :

...

Hope that helps.

Ah ok. So it seems that the ~ op comes from NumericalExpression, which you get from some magical implicit conversion from PrimitiveTypeMode after typing ~. The only reason you need it is because due to the magical nature of implicits, you never know for sure what any arithmetic/logical ops will resolve to. Using 'plus' or '~' ensures you get the right type. — Y.H Wong, Dec 18 '10 at 14:33

What does the SQueryL tilde operator do?

1 Answers1