0

My code is clunky:

  length: length? items
  count: 0
  foreach item items [
     count: count + 1
     if count = length [
        print "last item"
     ]
  ]

Is there something better ?

user310291
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1 Answers1

1

Typically people use FORALL (which would be much better named FOR-NEXT) which moves the series position as opposed to giving an item, then you can test it with TAIL?. The downside is you have to pick the item out of the series at the current position:

forall items [
    probe items/1 ;-- how to access current item
    if tail? next items [ ;-- could use LAST? ITEMS in Rebol 3
        print "last item"
    ]
]

This is approximately equivalent to:

 if not tail? items [
     original: items
     until [
         probe items/1
         if tail? next items [
             print "last item"
         ]
         items: next items
         tail? items
     ]
     items: original
 ]

Be forewarned: FORALL mutates its input series and tries to put it back to the initial position at the end. But it has poorly-defined behavior in the case of errors being raised, so you could leave your input in mid-iteration if there is a problem.

HostileFork says dont trust SE
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  • This does not work. Neither Rebol2 nor Red can print "last item", as the loop stops at the tail before the print statement. You should check at the next position **tail? next items** – sqlab Oct 27 '17 at 05:34
  • @sqlab Thanks, corrected. Note also that R3-Alpha has LAST? which might be good for Red to have also. – HostileFork says dont trust SE Oct 27 '17 at 11:18