Question

My interpretation of _._1 is:

_ = wildcard parameter
_1 = first parameter in method parameter list
But when used together with . what does it signify?

This is how its used :

.toList.sortWith(_._1 < _._1)

For this statement:

_++_

I’m lost. Is it concatenation two wildcard parameters somehow?
This is how its used:

.reduce(_++_)

I would be particularly interested if they above code could be made more verbose and remove any implicits, just so I can understand it better?

Answer 1

_._1 calls the method _1 on the wildcard parameter _, which gets the first element of a tuple. Thus, sortWith(_._1 < _._1) sorts the list of tuple by their first element.

_++_ calls the method ++ on the first wildcard parameter with the second parameter as an argument. ++ does concatenation for sequences. Thus .reduce(_++_) concatenates a list of sequences together. Usually you can use flatten for that.