Printing of array-valued elements

[Som Snytt]

Scala REPL goes to some length to pretty print appropriately. (Sorry, pun
alert.)

https://github.com/scala/scala/blob/2.11.x/src/library/scala/runtime/ScalaRunTime.scala#L321

Once the facility is available, many people ask how to get their arrays to
print like that.

There's a max line length which is usually hit before the max array length
to format. It's possible to bump the length from the REPL, because it's
annoying when the end of a lengthy result is clipped.

I like the idea of replacing a trailing ellipsis with the last few array
elements, at least for arrays of primitives. That's trickier for
deepToString.



On Thu, Aug 6, 2015 at 4:16 PM, Robert Field <robert.field at oracle.com>
wrote:

> As always in Java, there will be objects which only print out well when
> using a custom print method (which is easy to do in JShell), special-casing
> seems like complexity with payback that would rarely be used (or known to
> exist).
>
> -Robert
>
> > On Aug 6, 2015, at 12:53 AM, Ben Evans <benjamin.john.evans at gmail.com>
> wrote:
> >
> > Should "bigness" be a configurable parameter? I can see it being
> > irritating to have an array that is just too big to be printed out in
> > full.
> >
> > On Mon, Aug 3, 2015 at 10:13 PM, Jonathan Gibbons
> > <jonathan.gibbons at oracle.com> wrote:
> >>
> >>
> >> On 08/03/2015 12:31 PM, Brian Goetz wrote:
> >>>
> >>> The toString() method on arrays is generally unhelpful (inherited from
> >>> Object.)  Since jshell is a read-eval-PRINT loop, it might be nice to
> print
> >>> the result of array-valued expressions in a friendlier manner, such as
> by
> >>> using Arrays.toString(array) instead of array.toString(). (Might want
> to
> >>> limit this to arrays of below a certain length.  (Might want to allow
> that
> >>> limit to be set by preferences.))
> >>>
> >>> So we'd get
> >>>
> >>> [ 1, 2, 3 ]
> >>>
> >>> instead of
> >>>
> >>> [I at 2048230
> >>>
> >>
> >> If arrays are big, how about printing "the first few" and "the last
> few",
> >> separate by "...", as in
> >>
> >> [ 1, 2, 3, ..., 98, 99, 100 ]
> >>
> >> -- Jon
>
>