Small typo in original: should be .array~from(a.) GB
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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.
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.
Gil B.
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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--
Gil Barmwater
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