[REBOL] [REBOL] Default Port Values? Re:(3)
Want to add: You can 'probe for tracing, safe-close: func [p][if probe p [] [close probe p]] 'probe will show you the values without modifying something. good if one mistake content or the error-position. (thanks for the more specific answers for inits :) Volker Hi Ladislav: Yes, your code works for me. But I wrote a function as follows: safe-close: func [p[port!]][if p [close p]] lets say dufus: none safe-close dufus generates Script Error: safe-close expected p argument of type: port HOWEVER: if I write safe-close: func [p][if p [] [close p]] dufus: [] safe-close dufus I get no error message. :) Duh!! I know I have lots to learn yet. Thanks Tim Sorry, I don't understand. For me your code works: dufus-pointer: none == none either equal? dufus-pointer none [][close dufus-pointer] Ladislav
[REBOL] [REBOL] Default Port Values? Re:
Hi, Tim wrote: I'm setting up an object that contains some ports, which may or may not be open. i.e.: may or may not open "test.txt" may or may not open "dufus.txt" obviously I don't want to attempt to close what I didn't open. If I initialize a word to none as dufus-pointer: none and don't open it. the following code: either equal? dufus-pointer none [][close dufus-pointer] generates an error: expected argument of type: port similarly a function like safe-close: func [p[port!]][if p [close p]] generates an error message. How can I get around this? Thanks Folks! Tim Sorry, I don't understand. For me your code works: dufus-pointer: none == none either equal? dufus-pointer none [][close dufus-pointer] Ladislav
[REBOL] [REBOL] Default Port Values? Re:
Hi Tim, 1. safe-close: similarly a function like safe-close: func [p[port!]][if p [close p]] generates an error message. Since you only permit port! as the argument's datatype, and none is of type none! and not port!, you shouldn't be too surprised! ;-) Try safe-close: func [p[port! none!]][if p [close p]] safe-close: func [p[port! none!]][if p [close p]] safe-close dufus-pointer == false 2. equal? dufus-pointer none ... max's idea, to use port?, should certainly work (and is the cleaner way to do it anyway). It bothers me, however, that your code fails. The code you present should work as expected, as can easily be tested in the REBOL shell: dufus-pointer: none == none equal? dufus-pointer none == true I can think of three reasons why this could happen: 1. the error is not being generated by the code you presented; 2. dufus-pointer is being set (unexepctedly!) to some non-port value somewhere in your program. This possibility should worry you! ;-) 3. One of the two none values is not a none value. It is a word value. For instance: a: none == none b: first [none] == none none? a == true none? b == false type? a == none! type? b == word! At 08:44 PM 5/22/00 -0800, you wrote: I'm sending this again Are we having problems with the mailing list again? == I'm setting up an object that contains some ports, which may or may not be open. i.e.: may or may not open "test.txt" may or may not open "dufus.txt" obviously I don't want to attempt to close what I didn't open. If I initialize a word to none as dufus-pointer: none and don't open it. the following code: either equal? dufus-pointer none [][close dufus-pointer] generates an error: expected argument of type: port similarly a function like safe-close: func [p[port!]][if p [close p]] generates an error message. How can I get around this? Thanks Folks! Tim ;- Elan [: - )]
[REBOL] [REBOL] Default Port Values? Re:(2)
Hi Ladislav: Yes, your code works for me. But I wrote a function as follows: safe-close: func [p[port!]][if p [close p]] lets say dufus: none safe-close dufus generates Script Error: safe-close expected p argument of type: port HOWEVER: if I write safe-close: func [p][if p [] [close p]] dufus: [] safe-close dufus I get no error message. :) Duh!! I know I have lots to learn yet. Thanks Tim Sorry, I don't understand. For me your code works: dufus-pointer: none == none either equal? dufus-pointer none [][close dufus-pointer] Ladislav
[REBOL] [REBOL] Default Port Values? Re:(2)
Hi Max: That is very good advice. I keep forgetting to make use of rebol's run-time type checking. That is a very nice feature! Thanks Tim At 10:10 PM 5/22/00 -0700, you wrote: If port? dufus-pointer [ ]
[REBOL] [REBOL] Default Port Values? Re:(3)
Hi Tim, Here safe-close: func [p[port!]][if p [close p]] you are insisting that the argument to safe-close must be a value of datatype port!, [ p [port!] ]. Therefore you get an error message, whenever you pass a value that is not of type port!. In contrast, here safe-close: func [p][if p [] [close p]] you are not declaring a type restriction on the values passed to safe-close, [ p ]. Accordingly, safe-close does not complain that the value is not of type port!. Confusing? Not really. At 08:22 AM 5/23/00 -0800, you wrote: Hi Ladislav: Yes, your code works for me. But I wrote a function as follows: safe-close: func [p[port!]][if p [close p]] lets say dufus: none safe-close dufus generates Script Error: safe-close expected p argument of type: port HOWEVER: if I write safe-close: func [p][if p [] [close p]] dufus: [] safe-close dufus I get no error message. :) Duh!! I know I have lots to learn yet. Thanks Tim Sorry, I don't understand. For me your code works: dufus-pointer: none == none either equal? dufus-pointer none [][close dufus-pointer] Ladislav ;- Elan [: - )]
[REBOL] [REBOL] Default Port Values? Re:(2)
Hi Elan: Perhaps it is better to ask this question: What would be the preferred way to initialize a port prior to a possible open? would it best to be: my-port: none OR my-port: ;== It bothers me, however, that your code fails. The code you present should work as expected, as can easily be tested in the REBOL shell: dufus-pointer: none == none equal? dufus-pointer none == true I can think of three reasons why this could happen: 1. the error is not being generated by the code you presented; 2. dufus-pointer is being set (unexepctedly!) to some non-port value somewhere in your program. This possibility should worry you! ;-) 3. One of the two none values is not a none value. It is a word value. For Your concern is duly noted: If you're worried, I'm worried. Perhaps type? checking is the best way to go regards tj
