How to pattern match into an uppercase variable?

Question

I have a method in Scala that returns a tuple, let's say the method is called 'test'. Then I want to do

val (X,Y) = test()

However, the pattern-matching only works in Scala when the variable names are lowercase, ie:

val(_X,_Y) = test(); val X = _X; val Y = _Y

... works ok, but is ugly, and not terse. Since X and Y are matrices, I don't really want to have to use lowercase variables. (In scipy and matlab, I wouldn't have such a restriction for example).

I think there is some way to make sure lowercase variables behave like uppercase ones, ie by doing `x`. Perhaps there is some way of making uppercase variables behave like lowercase ones? So, that is my question: is there some way of pattern matching directly into uppercase variables in Scala?

Answer 1

The short answer is don't.

Syntax conventions make your code readable and understandable for others. Scala's convention is that variables start with lower-case and constants and classes start with upper-case. By violating this, not only you get problems like pattern-matching issues, your code becomes less readable. (Believe me, if you ever have to read code written by someone else who didn't care for such conventions, you'll be cursing that person.)

If you want to emphasize that the variables are matrices, I suggest you to use xMatrix and yMatrix or something like that. This will make clear that they're variables and that they represent matrices.

Or create a convention specific to your project that all matrix variables will end with let's say "M", like xM and yM.

It's worth typing a few more characters if it makes your code readable.

Answer 2

There is no way to do this and there shouldn't be. You already have the type of the variable to tell you that it is a matrix, so there is no need to make variable names uppercase.