On 02.03.2013 20:03, vrt277 wrote:
Implementation of anonymous methods was started in the branch. Author
didn't submit anything last year and forgot commit one added file. But
changes from branch can be useful, AFAIU parsing of anonymous functions
without capturing of local variables was implemented.
Does someone know is author available? Does he plan to continue work, or
I can work on implementation without collaboration with him ? Or at
least can he send missed file ?
I have already written the author some time ago. He has said that he
plans to at least commit the missing files. If you would continue his
work (in a new branch please with a complete copy of trunk...) then he
might be relieved as well.
It's hard to properly split this complex task into subtasks. I can
propose 2 steps:
1. Parsing and generation of anonymous function. Capturing of
variables is forbidden.
2. Capturing of variables is implemented.
A question for fpc team: do you agree that support of Delphi-compatible
anonymous methods should be implemented?
At least I do, yes.
Also there are open questions which require brainstorm:
1. Does Pascal needs other implementation of closures which is different
from anonymous methods implementation?
I would say no. After all the method implementation itself stays the
same, but the captured variables should be different. Or what does this
print:
=== example begin ===
var
arr: array[0..5] of reference to procedure;
i: LongInt;
begin
for i := Low(arr) to High(arr) do
arr[i] := procedure
begin
Writeln(i);
end;
Writeln('Output: '); // just to ensure that the optimizer doesn't
combine the two loops
for i := Low(arr) to High(arr) do
arr[i]();
end;
=== example end ===
2. Does Pascal needs short syntax for closures?
I would say yes, but this can be done in a seperate step
I if someone want to discuss these questions it will be better to create
in separate threads.
Two personal things I'd like to note as I have already planned to
continue working on anonymous functions myself:
- add support to pass nested functions to "reference to" procvars; this
will allow users who don't want to use the anonymous syntax to use the
"closure" feature as well; please note that this must be done in a way
that passing nested functions to "is nested" procvars is not broken
- (in context with the above point) couple the support for the anonymous
functions to a new modeswitch (enabled by default in mode delphi), but
allow "reference to" procvars in non-Delphi modes (this way you'd only
be able to use nested functions, but later on the shorter syntax should
be used there as well)
Regards,
Sven
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