check conditions one by one and execute corresponding block accordingly

---

Parameters

when conditions :block

Attributes

any		check all conditions, without breaking, regardless of success
has	:any	prepend given value to each of the conditions

Returns

Examples

copy
; the main block is always evaluated!
when [
    prime? 4 -> print "yes, 4 is prime - wait, what?!"
    prime? 5 -> print "yes, 5 is prime"
    prime? 7 -> print "yes, 6 is prime"
    true     -> print "none of the above was true"
]
; yes, 5 is prime

copy
when.any [
    prime? 4 -> print "yes, 4 is prime - wait, what?!"
    prime? 5 -> print "yes, 5 is prime"
    prime? 7 -> print "yes, 7 is prime"
]
; yes, 5 is prime
; yes, 7 is prime

copy
x: 2
when.has: x [
    [=0] -> print "x is zero!"
    [<1] -> print "x is less than 1"
    [<4] -> print "x is less than 4"
    true -> print "x is >= 4"
]
; x is less than 4

copy
f: function [x][
    print ["called F with:" x]
    return odd? x
]
; short-circuiting:
; conditions are not evaluated unless needed
when [
    [f 10]-> print "F 10"
    [f 11]-> print "F 11"
    [f 12]-> print "F 12"
]
; called F with: 10 
; called F with: 11 
; F 11

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