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19-Apr 5:51 UTC
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Mailing List Archive: 49091 messages
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How to check validity of types ?

 [1/4] from: coussement::c::itc::mil::be at: 15-Jan-2001 10:44


Hi REBOLs, I would like to check if a provided value meets pre-defined type requirements... So I define the valid types into a block 'b:
>> b: [integer! string!]
== [integer! string!]
>> first b
== integer!
>> value: make integer! 1
== 1
>> type? value
== integer! And I check the requirement:
>> (type? value) = first b
== false Of course the assumed answer was 'right... What did I wrong ? Is there another way to get what I want ? Any idea, suggestion ? thx a lot for answering CU, chr==

 [2/4] from: brett:codeconscious at: 15-Jan-2001 21:51


Hi Christophe,
> So I define the valid types into a block 'b: > > >> b: [integer! string!] > == [integer! string!] > >> first b > == integer!
You didn't get what you thought you got here. What you actually got was the word "integer!" not the datatype integer!
>> type? first b
== word! Why? Blocks contain unevaluated data.
> >> value: make integer! 1 > == 1
<<quoted lines omitted: 6>>
> What did I wrong ? Is there another way to get what I want ? Any idea, > suggestion ?
What you need is a reduce on the line. Try this instead
>> b: reduce [integer! string!]
== [integer! string!]
>> type? first b
== datatype!
>> first b
== integer!
>> value: make integer! 1
== 1
>> (type? value) = first b
== true Also note that functions can check the datatypes of their parameters.
>> my-integer-function: func [an-int [integer!] ] [ an-int * 5] >> my-integer-function "test"
** Script Error: my-integer-function expected an-int argument of type: integer. ** Where: my-integer-function "test" And remember parse in block mode can check datatypes as well. Dialects don't have to be long!
>> parse [3] [integer!]
== true
>> parse ["test"] [integer!]
== false Brett.

 [3/4] from: rebol:techscribe at: 15-Jan-2001 11:05


Hi Christian, the reason you get this behavior is that the words in the block, [integer! string!], are not bound to the REBOL global context. Simply say b: reduce [integer! string!] and that will do the trick. When you reduce the block REBOL binds the words to the global context and now integer! = first b == true, and string! = second b == true as well. Hope this helps, Elan CRS - Psy Sel/SPO, COUSSEMENT Christophe, CPN wrote:

 [4/4] from: coussement:c:itc:mil:be at: 16-Jan-2001 9:10


Thanks Elan. So stupid of me I didn't think about that ;-( chr==
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