Why can I use lower-case letters for names:
val (a, bC) = (1, 2)
(1, 2) match {
case (a, bC) => ???
}
and can't use upper-case letters:
/* compile errors: not found: value A, BC */
val (A, BC) = (1, 2)
/* compile errors: not found: value A, BC */
(1, 2) match {
case (A, BC) => ???
}
I'm using scala-2.11.17
Because the designers of Scala preferred to allow identifiers starting with upper-case letters to be used like this (and allowing both would be confusing):
val A = 1
2 match {
case A => true
case _ => false
} // returns false, because 2 != A
Note that with lower case you'll get
val a = 1
2 match {
case a => true
case _ => false
} // returns true
because case a
binds a new variable called a
.
One very common case is
val opt: Option[Int] = ...
opt match {
case None => ... // you really don't want None to be a new variable here
case Some(a) => ...
}
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