[REBOL] Ifs Re:
From: joel:neely:fedex at: 11-Oct-2000 16:20
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 [joel--neely--fedex--com] 901-263-4460 38017/HKA/9677
REBOL [] print to-string debase decompress #{
789C0BCE0BAB4A7176CA48CAB53448740FABF474F3720BCC
B6F4F574CFC888342AC949CE74B50500E1710C0C24000000}
