Extend @show: allow multiple args, return value of last

[toivoh]

This patch extends the @show macro in two ways, to make it more handy in debugging:

• Multiple arguments are allowed, e.g.

  x, y = 3, 4
  @show x y
  

  prints

  x   = 3
  y   = 4
  

• The value of @show is the value of it's last argument. Using this, @show can be inserted pretty much anywhere in an expression to produce a printout, e.g.

  f(args...) = some_computation_based_on_args
  

  can be rewritten to print out its return value like

  f(args...) = @show some_computation_based_on_args
  

  instead of

  function f(args...)
      result = some_computation_based_on_args
      @show result
      result
  end
  

I haven't come up with a case where it makes much sense to use both features at the same time. If anyone thinks that the value of @show with several arguments should be something else, please let me know.

[ViralBShah]

This looks good to me. Any other views?

Also, needs a rebase for merging, assuming there are no other views.

[toivoh]

I see that @StefanKarpinski already did the multiple arguments part. I've written a new patch on top of his.

[StefanKarpinski]

Sorry about that – I missed this patch.

[toivoh]

No worries.

[toivoh]

Ok, so good to merge?