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[REBOL] Re: Confusion on when a block gets evaluated

From: tim-johnsons:web at: 6-Mar-2006 17:07

* Peter Wood <> [060305 21:34]:
> Jeff > > Ladislav Mecir's excellent "essays" may help, particularly > > > You can access Ladislav's other work via >
You can also use the rebol word unset? which is a predicate that checks to see if a value is unset. example:
>> unset? print "yes"
yes == true This is useful when using a loop to accumulate values. You can use to first check to see something is unset before adding it to whatever you are using to accumulate the values. I generally use unset? inside of small functions, using it by itself, has caused me some heartburn in the past. example: =s: func [ "Check for unset or none values and return an empty string if found" v [any-type!] ][ either unset? get/any 'v [""] [any[v ""]] ] ;; end function In the interpreter window, enter
>> help unset?
;; and
>> help get
-- Tim Johnson <>