Re^5: Using lazy list with a for loop

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Re^6: Using lazy list with a for loop by ikegami (Patriarch) on Jan 03, 2023 at 04:18 UTC
That has all the problems of the `each` builtin. Better to have a generator creator and user. `my $iter = $api->get_widgets_iter(); while ( my ( $widget ) = $iter->() ) { ... }` [download]	[reply] [d/l] [select]
Re^7: Using lazy list with a for loop by LanX (Saint) on Jan 03, 2023 at 15:24 UTC
I agree there are some edge cases to consider depending on the use-case... and I don't know the OPs use cases good enough. But because of cleaner scope and loop-control statements I'd rather prefer `for (my $iter = get_iter(); my ( $widget ) = $iter->(); ) { ... }` [download] over `my $iter = get_iter(); while ( my ( $widget ) = $iter->() ) { ... }` [download] This approach will put $iter in a tight scope and properly destroy. Needless to say, if Perl had macros like Lisp, we wouldn't need to repeat that discussion again and again... Keyword-simple could solve this, but is restricted to statements only. see also Can I check if a loop's scope is entered for the first time? Cheers Rolf _{(addicted to the 𐍀𐌴𐍂𐌻 Programming Language :) Wikisyntax for the Monastery}	[reply] [d/l] [select]
Re^8: Using lazy list with a for loop by ikegami (Patriarch) on Jan 03, 2023 at 16:26 UTC
I agree there are some edge cases to consider depending on the use-case... Code that fails subtly when an exceptions or next/last is occurs? It's not a question of if it's going to bite you, but when.	[reply]
Re^6: Using lazy list with a for loop by Anonymous Monk on Jan 03, 2023 at 04:16 UTC
hence you need to switch to while and add an iterator method ->each to your API ° `while (my ($widget) = $api->each( $item->{sets}{widgets})) { ... }` [download] That would now be the ideal for me, but don't you need to instantiate the iterator before calling it? Like: `my $iter = $api->each( $item->{sets}{widgets} ); while (my ($widget) = $iter->()) { ... }` [download] I wonder if you can combine the intializer with the iterator in a single call and have it rebless itself on the first call. Algorithm::Combinatorics does something similar.	[reply] [d/l] [select]
Re^7: Using lazy list with a for loop by LanX (Saint) on Jan 03, 2023 at 15:32 UTC
depending on your use cases, yes. for instance you could bind the iterator to the code-line where it is first invoked like available via `caller` the next question is if the iterator needs to be destroyed because you leave the loop via `last`. otherwise an inner loop wouldn't notice if it is reentered. For instance, an (IMHO extreme) requirement would be to properly support `redo` In order to cover all use cases you would need `for (my $iter = create(...); my ($value) = $iter->get(); $iter->inc() +) { ...BODY... }` [download] as I said, not easy. Cheers Rolf _{(addicted to the 𐍀𐌴𐍂𐌻 Programming Language :) Wikisyntax for the Monastery}	[reply] [d/l]