Boggled with scala.util.matching.Regex

[mar]

With these defined..

scala> val t = "this is a test"

t: java.lang.String = this is a test

scala> val rx = " ".r

rx: scala.util.matching.Regex =

0

This works:

scala> val m = rx.findAllIn(t)

m: scala.util.matching.Regex.MatchIterator = non-empty iterator

scala> m.end

res01: Int = 5

.. while this doesn't:

scala> rx.findAllIn(t).end

java.lang.IllegalStateException: No match available

.findAllIIn produces a MatchIterator which has an end-method defined. I fail to see why the last example fails.. :\

[Daniel Sobral]

Bizarre, I admit, but there's an explanation. The method findAllIn
returns an Iterator -- you need to iterate over it to interact with
it. In the first case, the REPL called "toString" on it, which got it
to check the existence of the first element. In the second case, you
called a method directly without first asserting the existence of the
element.

IMHO, having MatchIterator extend MatchData was a bad design decision
-- Iterators should be Iterators, not Data. As bad design decisions
go, however, this one is mostly harmless -- it mostly breaks broken
code.

--
Daniel C. Sobral

I travel to the future all the time.

[mar]

That's a great explanation, thank you. A sure "gotcha" if I ever saw one :)

[Daniel Sobral]

I'm sending this one to Scala Puzzlers! (http://scalapuzzlers.com/index.html)