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<font size="4"><font face="monospace">(cross-posting to -comments is
discouraged)<br>
<br>
If we are reconstructing something as trivial as a Point, we
might not even use a reconstruction expression, since an
ordinary constructor invocation is probably good enough (it only
has two components, and we're changing at least one of them.) <br>
<br>
Now imagine you are reconstructing something with a dozen
components, which is where reconstruction expressions offer more
value. I don't think people would be very happy with a syntax
like<br>
<br>
thingie with Thingie(var a, var b, var c, var d, var e, <br>
var f, var g, var h, var i, var j) { a
= 3 }<br>
<br>
<br>
</font></font><br>
<div class="moz-cite-prefix">On 10/18/2023 8:01 PM, David Alayachew
wrote:<br>
</div>
<blockquote type="cite" cite="mid:CAA9v-_OMrqnnHx5=Zaw4Y_yxPKE5VvvVnm=m5ALsBNVR0shHow@mail.gmail.com">
<div dir="ltr">
<div class="gmail_default" style="font-family:monospace">Also
adding <a class="gmail_plusreply" id="plusReplyChip-1" href="mailto:amber-dev@openjdk.org" tabindex="-1" moz-do-not-send="true">@amber-dev</a> <br>
</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Wed, Oct 18, 2023 at
8:00 PM David Alayachew <<a href="mailto:davidalayachew@gmail.com" moz-do-not-send="true" class="moz-txt-link-freetext">davidalayachew@gmail.com</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div dir="ltr">
<div class="gmail_default" style="font-family:monospace">Adding
-comments<br>
</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Sat, Sep 23, 2023 at
10:54 AM Attila Kelemen <<a href="mailto:attila.kelemen85@gmail.com" target="_blank" moz-do-not-send="true" class="moz-txt-link-freetext">attila.kelemen85@gmail.com</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
<div dir="ltr">Note: I think you would have a better
chance, if you sent the email to "amber-spec-comments"
than "observers", since the people who can actually make
changes are more likely to read the "comments" list.
<div><br>
</div>
<div>That said, I don't really see the usefulness of
such a syntax (and adding new syntax in itself is a
detriment). That is, if I understood you correctly,
then your example would replace this:</div>
<div><br>
</div>
<div>```</div>
<div>Point p = ...;<br>
Point pp = new Point(p.x() + 2, 0);<br>
</div>
<div>```</div>
<div><br>
</div>
<div>which is shorter and a lot more obvious. And if we
were to go to more complicated things (many
properties), then it doesn't help that much, because
as far as I understand you, your proposal is still
positional in its deconstruction pattern, and the
positional nature is usually what is awkward in
structures with many properties.</div>
<div><br>
</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">Harrison Chikwe <<a href="mailto:nhcdeveloper@gmail.com" target="_blank" moz-do-not-send="true" class="moz-txt-link-freetext">nhcdeveloper@gmail.com</a>>
ezt írta (időpont: 2023. szept. 23., Szo, 12:01):<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px
0px 0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
<div dir="ltr">
<div>Hi,</div>
<div><br>
</div>
<div>I think that it is very useful to have when
working with immutable objects.</div>
<br>
For the purposes of this mail, let's call the design
described in the ambro-doc[1]:<br>
reconstruction expression with implicit
deconstructor (aka REWID).<br>
<br>
Has it been considered to make the deconstructor
pattern explicit in the reconstruction<br>
expression (aka REWED)?<br>
Doing so may remove the requirement to make names
more significant in the language.<br>
<br>
For example, given the following:<br>
<br>
Point p = ...;<br>
Point pp = p with(int x, int y) { x += 2; y = 0; }<br>
<br>
We can interpret the reconstruction expression above
as:<br>
<br>
. Find a deconstructor and constructor pair that has
a signature that matches (int, int)<br>
. Deconstruct the target with the deconstructor<br>
. Execute the block on RHS<br>
. Invoke the constructor with the result.<br>
<br>
If we split the reconstruction expression into three
steps:<br>
<br>
1. Extraction<br>
2. Transformation<br>
3. Construction<br>
<br>
In REWID users are required only to do step 2
(transformation) and the<br>
system handles 1 and 3. Whereas in REWED users are
required to do step 1 and 2<br>
and the system handles just step 3.<br>
<br>
# Other forms of REWED<br>
<br>
1. Explicit Named deconstructor pattern<br>
<br>
Point pp = p with Point(int x, int y) {...}<br>
<br>
2. Explicit Var deconstructor pattern<br>
<br>
Point pp = p with var(int x, int y) {...}<br>
<br>
3. Explicit Unnamed deconstructor pattern<br>
<br>
Point pp = p with(int x, int y) {...}<br>
<br>
<br>
We can extend form 1 to include factory pattern:<br>
<br>
Point pp = p with Point.factory(int x, int y)
{...}<br>
<br>
<br>
# Advantages<br>
<br>
1. No need to make names significant.<br>
2. Can be combined with other patterns (e.g. unnamed
pattern, var pattern)<br>
<br>
Point pp = p with(int x, _) { x = 0; }<br>
<br>
<br>
Nyehamene.</div>
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