Scala complication. Variable reassignment

Question

I'm trying to understand how Scala works. So I typed this code.

var name = "eMmanuel"
val n = name.exists(_.isUpper)

name = "book"

Just looking at it, in my mind, I expect n to be true, I compile this and n: Boolean = true, which is understandable. But in the console I see something strange.

name: String = book
n: Boolean = true
name: String = book

After compilation, first line of results from console tells me name: String = book now, if name is now String = book why is n: Boolean = true? Shouldn't this be false? because after all, it's showing name: String = bookwhich obviously has no capital letter in it!

Are you actually re-evaluating the second line? Because the result stored in n is not lazy, it will only be calculated once. — danielkza
– danielkza, Commented Dec 18, 2013 at 12:38

Community · Accepted Answer · 2017-05-23 11:50:16Z

5

I'm assuming name = book is actually name = "book".

n will have an unchanged value because it is a val. A val gets only evaluated once, on assignment (there are also lazy vals that are evaluated on first dereference). See e.g. here for more information.

In your specific case, it looks like you wanted n to be evaluated each time, which means you need to declare n as a def, i.e.:

def n = name.exists(_.isUpper)

This will create a no-argument method, evaluated every time you invoke n.

edited May 23, 2017 at 11:50

CommunityBot

11 silver badge

answered Dec 18, 2013 at 12:27

mikołak

9,7151 gold badge50 silver badges71 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Scala complication. Variable reassignment

1 Answer 1

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related