Another observation.
After BSF4ooRexx gets based on Java 1.6/6.0 I have started to work on extending
DO...OVER for
java.lang.Iterable, java.util.Enumeration, java.util.Collection,
java.util.Iterator and
java.util.Map to make it transparent for Rexx programmers what kind of a Java
collection is being
worked upon.
For this support ooRexx MAKEARRAY and SUPPLIER messages will cause the
respective Rexx array and
supplier objects to be returned.
In the case of a Java array, there is an ooRexx wrapper class named
"BSF_ARRAY_REFERENCE" which
implements all relevant Rexx array methods, namely: "AT", "[]", "DIMENSION",
"ITEMS", "PUT", "[]=",
"SIZE" (so to say the Rexx array protocol). Although it is true, that it is not
a subclass of ooRexx
.Array, it is a compatible implementation where the ooRexx Array protocol gets
satisified.
Rexx/ooRexx being deliberately a dynamic language should allow to process
BSF_ARRAY_REFERENCE (or
any other type of) objects in place of genuine ooRexx array objects as long as
the ooRexx Array
protocol (its Array methods) are present.
This is probably more a feature request, a request for discussion, than
anything else.
---rony
On 06.11.2016 15:34, Rony G. Flatscher wrote:
>
> The DO...OVER statement allows one to iterate over a collection. To do so a
> MAKEARRAY is requested
> and the resulting array is then iterated over.
>
> It seems, that the code in DO...OVER does not send the MAKEARRAY message, if
> it does not find that
> method in the receiver object, irrespectible whether an UNKNOWN method is
> available that may step
> in and return that array upon request.
>
> Here is a Rexx program demonstrating this problem, bug:
>
> t=.test~new tArr=t~makearray~toString(,"/") say "tArr:" tArr do o over t
> say o end say "---"
> u=.uuu~new uArr=u~makearray~toString(,"/") say "uArr:" uArr do o over u
> say o end say "---" *::class test ::method makearray*return ("one", "two",
> "three") *::class uuu****::method
> unknown* use arg methName, methArgs /*if methName="MAKEARRAY" then return
> ("one", "two",
> "three")*/ say "in" self"::unknown, about to raise a syntax condition"
> raise syntax 98.913
> array (self)
>
> The class "TEST" implements the MAKEARRAY method and the DO...OVER succeeds.
>
> The class "UUU" does not implement the MAKEARRAY method, but an UNKNOWN
> method that returns an
> array, if a MAKEARRAY message was received. Here, DO...OVER causes a 98.913
> syntax error, which
> aborts the program!
>
> Here is the output of running the above program:
>
> F:\test\oorexx\makearray>test1 tArr: one/two/three one two three ---
> uArr: one/two/three 13
> *-* do o over u Error 98 running F:\test\oorexx\makearray\test1.rex line
> 13: Execution error.
> Error 98.913: Unable to convert object "an UUU" to a single-dimensional
> array value.
>
> It may be the case that the interpreter tries to optimize by checking for the
> existence of a
> MAKEARRAY method in the receiving object and if not found short-circuiting by
> raising the syntax
> error. Instead it should let the UNKNOWN mechanism to get exercised, such
> that it becomes possible
> to delegate the execution of such unknown messages (like MAKEARRAY in the
> class UUU above) by
> other code, which is the purpose of the UNKNOWN mechanism in the first place.
>
> This is with ooRexx 5.0.0 beta, not sure about previous versions.
>
> If there are no counter arguments, then I will file a bug report for this in
> the tracker.
>
> ---rony
>
> P.S.: "DO WITH index i and item o" works by supplying the SUPPLIER method
> explicitly or implicitly
> by the UNKNOWN method. Here is an example for that variant:
>
> t=.test~new say "tArr:" tArr do with index idx item o over t say "index:"
> idx "item:" o end
> say "---" u=.uuu~new say "uArr:" uArr do with index idx item o over u say
> "index:" idx "item:"
> o end say "---" *::class test* *::method supplier* return
> .supplier~new((1,2,3), ("one",
> "two", "three")) *::class uuu****::method unknown* use arg methName,
> methArgs /*if
> methName="SUPPLIER" then return .supplier~new((1,2,3), ("one", "two",
> "three"))*/ say "in"
> self"::unknown, about to raise a syntax condition" raise syntax 98.913
> array (self)
>
> Output (no runtime error):
>
> F:\test\oorexx\makearray>test2 tArr: TARR index: one item: 1 index: two
> item: 2 index: three
> item: 3 --- uArr: UARR index: one item: 1 index: two item: 2 index: three
> item: 3 ---
>
>
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