[REBOL] Ifs Re:

[joel . neely]

Hi, all...

In honor of the newest REBOL book (and for those of us who can't count to
three in proper order, such as myself! ;-) and inspired by the keywords
feature of Common Lisp, I offer yet another   ifs   , which doesn't care
in which order the actions are specified:

  >> a: 1
  == 1
  >> ifs-for-dummies a [positive: ["plus"] zero: ["zip"] negative: ["minus"]]
  == "plus"
  >> ifs-for-dummies a [zero: ["zip"] positive: ["plus"] negative: ["minus"]]
  == "plus"
  >> ifs-for-dummies a [negative: ["minus"] zero: ["zip"] positive: ["plus"]]
  == "plus"

whether they are all specified:

  >> ifs-for-dummies a [positive: ["biggerthanzero"]]
  == "biggerthanzero"
  >> ifs-for-dummies a [negative: ["smallerthanzero"]]
  >> ifs-for-dummies a [zero: ["equaltozero"]]
  >> ifs-for-dummies a [zero: ["equaltozero"] positive: ["bigger, again!"]]
  == "bigger, again!"

or whether the selector has unstable side-effects:

  >> a: 1
  == 1
  >> b: to-paren [a: 0 - a]
  == (a: 0 - a)

  >> ifs-for-dummies b [negative: ["minus"] zero: ["zip"] positive: ["plus"]]
  == "minus"
  >> ifs-for-dummies b [negative: ["minus"] zero: ["zip"] positive: ["plus"]]
  == "plus"
  >> ifs-for-dummies b [negative: ["minus"] zero: ["zip"] positive: ["plus"]]
  == "minus"
  >> ifs-for-dummies b [negative: ["minus"] zero: ["zip"] positive: ["plus"]]
  == "plus"

This new candidate (which will run if evaluated, but not if elected), has a
running mate:

  fortranif: make object! [
      positive: []
      negative: []
      zero:     []
      selector: 0
      compute:  func [[throw] selexpr] [
          selector: selexpr
          either positive? selector [
              do positive
          ][
              either negative? selector [
                  do negative
              ][
                  do zero
              ]
          ]
      ]
  ]

and a campaign promise:

  ifs-for-dummies: func [[throw] selexp conseq [block!] /local actor] [
    actor: make fortranif conseq
    actor/compute selexp
  ]

(In case you're wondering, the news coverage of the US election campaigns
hasn't affected me at all!  "My fellow REBOLians...")

-jn-

"Coding at the speed of a dummy!"

-- 
; Joel Neely  [EMAIL PROTECTED]  901-263-4460  38017/HKA/9677
REBOL []  print to-string debase decompress #{
    789C0BCE0BAB4A7176CA48CAB53448740FABF474F3720BCC
    B6F4F574CFC888342AC949CE74B50500E1710C0C24000000}