On 2023-01-07 07:02:33 Rony G. Flatscher wrote:
> On 07.01.2023 00:00, J Leslie Turriff wrote:
> > On 2023-01-03 04:25:33 Rony G. Flatscher wrote:
> >> Thanks to everyone for the comments, information and ideas. Enclosed
> >> please find the next iteration of that little script. Invoking it with
> >> "getOoRexxDocs.rex ?" yields the refurbished (hopefully clearer) usage
> >> text:
> >>
> >> getOoRexxDocs.rex [directory [needle]]
> >>
> >> a utility to download the ooRexx documentation
> >> from SourceForge and save them in a subdirectory "docs.V" of the current
> >> directory where "V" is the specified version (e.g. "5.0.0")
> >>
> >> no argument ... download all files from the directory
> >> carrying the highest version number
> >>
> >> ? or -h ... show this usage information
> >>
> >> directory ... the SourceForge documentation directory to
> >> download from, usually named after the ooRexx version (e.g. "4.2.0",
> >> "5.0.0", "5.1.0beta")
> >>
> >> needle ... only downloads files from the SourceForge
> >> directory which contain the (caseless) needle in their names (e.g.
> >> "-html.zip", ".pdf", "ref")
> >>
> >> N.B.: This program uses "curl" on all platforms. You can find more
> >> information on the Internet or<https://curl.se>
> >> and<https://en.wikipedia.org/wiki/CURL>.
> >
> > [snip]
> >
> >> Any feedback, ideas?
> >>
> >> ---rony
> >
> > I'm curious as to where you obtained the shortcut .resources syntax used
> > in the usage handler in this program? It is simply
> >
> > | say .resources~usage
> >
> > but the Language Reference only shows
> >
> > | say .resources[name]~makeString
> >
> > which is harder to remember.
>
> There are a few things here to know:
>
> * ooRexx is influenced by Smalltalk quite a bit and incorporates the
> message paradigm of which Alan Kay (https://de.wikipedia.org/wiki/Alan_Kay,
> German, but cites Alan Kay in English near the top from
> https://en.wikipedia.org/wiki/Alan_Kay) says: "I'm sorry that I long ago
> coined the term "objects" for this topic because it gets many people to
> focus on the lesser idea. The big idea is "messaging". In ooRexx there is
> an explicit message operator, the tilde (~), left of which is the receiver
> and right of it the name of the message.
>
> o In principle, if a programmer wishes that a method routine gets
> executed he has to send the value (a.k.a. "object", "instance") a message
> by the name of the desired method routine; the receiving object (a.k.a.
> "value", "instance") conceptually then looks up the inventory of method
> routines in its class (a.k.a. "type", "structure") and invokes it on behalf
> of the programmer and returns any result the method routine may produce (ff
> the message carries arguments they get used when the receiving object
> invokes the method routine).
>
> o If the receiver cannot find a method routine named after the
> message, it will look-up its super class and look there and if not found in
> its superclass and so forth until the root class (named "Object") has been
> sought. If no matching method routine is found, then a runtime error gets
> created with the message "97.1 Object xyz does not understand message mno"
> and the program gets stopped.
>
> However, there is an "unknown" mechanism built-into ooRexx: before
> raising the syntax error 97.1 a search for a method routine named "unknown"
> is excercised as above. Should such a method routine be available then the
> receiver will invoke it instead and supply two arguments, the name of the
> message in uppercase and an array that contains the arguments, if any,
> supplied with the message.
>
> In the case of resource directives ooRexx creates a collection (of
> type StringTable which is like the ooRexx Directory) named "RESOURCES" and
> saves it in the package's (package is a normal Rexx program that usually
> happens to have directives) environment directory and can then be
> referenced by its environment symbol (an environment symbol always starts
> with a dot) '.RESOURCES' . ooRexx then saves each resource directive there
> using as the index the name (in uppercase) and the contained lines as an
> array. In the program the name of the resource is "usage", hence one can
> fetch that entry from .resources with ".resources['USAGE']".
>
> Now, the StringTable (like the Directory) class have an unknown
> method routine defined (cf. rexxref.pdf, "5.3.17.22. unknown", "5.3.9.23.
> unknown") for them. This unknown method will use the received unknown
> message name as the index and look-up itself using that value. So if one
> sends ".resources~usage" the StringTable unknown method routine will get
> "USAGE" and use that to look up the StringTable and return the stored array
> (for more information look up the reference manual).
>
> * REXX is a string based language, such that everything is a string.
> ooRexx in order to remain backwardly compatible (becoming able to execute
> REXX programs as well) makes sure that REXX BIFs (built-in-functions) and
> REXX keyword statements like SAY or PARSE get strings to work with, even if
> they get values supplied that are not strings like is the case with a value
> of type Array. So what happens in this case is that the SAY keyword
> instruction requests a string value from the array value/object/instance
> and gets it magically. ;) Actually, there is no magic involved in this, one
> just needs to know one more thing in this context: each
> class/type/structure in ooRexx possesses a method routine named "STRING"
> (this method routine is defined in the root class named "Object", cf.
> rexxref.pdf, "5.1.4.25. string") which will return a string value (usually
> that string value contains the name of the class/type/structure the
> value/object/instance got created from). If however there is in addition a
> method named "MAKESTRING" available, then that is executed which is the
> case for Array collections (cf. rexxref.pdf, "5.3.6.24. makeArray").
>
> You may want to look up rexxref.pdf, "4.2.11. Required String Values".
>
> HTH,
>
> ---rony
Okay, I see now. I wonder, though, if relying on method UNKNOWN as a
shortcut might be a
bit dangerous, if the underlying code gets changed sometime in the future?
Leslie
--
Platform: GNU/Linux
Hardware: x86_64
Distribution: openSUSE Leap 15.4
Open Object Rexx: 5.0.0 r12286
Build date: Aug 12 2021
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