Hi Gil,
On 09.03.2025 14:45, Gilbert Barmwater wrote:
Many years ago, I saw the same need but in a more general context, converting an instance of an
ordered collection to a different collection type. And, yes, I know that stems are NOT ordered
collections!
The .list, .queue, .circularqueue (and .array) all have a makearray method. So the first thought
was to create a makelist, makequeue and makecircularqueue methods for all the classes. Then it
occurred to me that by adding a class method to the orderedcollection class, which I called
'from', I could achieve the same thing. So, for example, if you have an array named arr, then
.list~from(arr) would create an instance of .list containing all the items in arr in the same
order. The advantage is that a single method needs to be added and, by inheritance, all four of
the ordered collection classes get the new functionality.
Since one of the most frequent uses of stems is to implement a (stem) array, extending the idea to
that class seemed logical. Then one could code .stem~from(arr) and conversely .array~from(.a).
This requires an addition to the stem class of a 'from' class method and changes to the 'from'
ordered collection method to handle stem instances. And, yes, the edge cases mentioned in this
thread need to be handled as well.
Sounds interesting!
The edge case for .stem, keeping the current makeArray semantics and allowing for the "stemArray"
semantics (maybe as a second argument?), would be a nice show case perhaps.
I implemented this both in a private build and via sub-classing and it has worked well for me for
a long time. I strongly recommend this approach to the problem and am happy to share my
implementation if the development community decides to open an RFE.
Will do to get to see your implementation, thanks for the offer! :)
Cheers
---rony
On 3/9/2025 6:39 AM, Rony G. Flatscher wrote:
1) ad stem arrays
==============
Stem arrays have been conceived and used since the inception of Rexx.
The pattern is simple: the tail is an integer number from 1 on, the tail with the value 0 keeps
the current number of total stem array elements. E.g.:
a.1="one"
a.2="two"
a.0=2
say "there are" a.0 "items"
Turning such a stem array into an ooRexx array should yield an array that omits the element with
the tail 0 and uses the tail's number as index in the ooRexx array. E.g. turning the above stem
array into an ooRexx array:
a[1]="one"
a[2]="two"
say "there are" a~itmes "items"
1a) In order to create an ooRexx array from a stem array the following method should be added to
the stem class:
makeArrayFromStemArray
This name makes it clear that a stem array is to be processed and that the resulting array should
not have the stem value with the tail 0.
(The existting stem method makeArray continues to create an array that represents all tails of a
stem, including a tail with the value 0.)
1b) In order to create a stem from an ooRexx array the following method should be added to the
array class:
makeStemArray
This name makes it clear that a stem array is to be created from the array items (using the array
index values as tails) and adding the 0 tail to indicate the number of stem elements.
---
2) ad using the array class for reading and writing files/streams directly
==========================================================
The ooRexx stream class has a method arrayin to allow reading the content of a stream into an
ooRexx array, and arrayout to write the content of an array to a stream. In order to use these
methods a stream instance must be created first before being able to use the arrayin and arrayout
methods and closing the stream thereafter. As the purpose of these two methods is to simply get
the content into and from an array, it may be cumbersome to explicitly have to open and close
streams in order to just read into or write the content of an array.
In order to forego the need to create stream instances in order to read the content into an array
or an array into a stream or file two class methods for the ooRexx array class are proposed:
2a) In order to read the content of a stream or a file with a single message into an array the
following method should be added to the array class:
arrayin(filename|stream|file[, Lines|chars)
This allows for supplying either a filename (string), an instance of .File or .Stream and
optionally "Lines" (default, one array element per text line) or "chars" (one array element per
character).
2b) In order to write the content of an array to a file or a stream the following method should
be added to the array class:
arrayOut(filename|stream|file[, Lines|chars)
This allows for supplying either a filename (string), an instance of .File or .Stream and
optionally "Lines" (default, a text line per per array element) or "chars" (the characters of all
array elements, without appending endoflines).
---
Any comments, thoughts?
---rony
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