Re^2: Using x to build data structures considered harmful

It turns out that the best way I can think of to do that (in the general case) is my @testData = map {int rand(1000)} 0..1_000_000;, which isn't as readable (but does have the advantage of working).

This makes me wonder if I should bring it up on perl6-language, as I know of no better way to do it there.

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Re^3: Using x to build data structures considered harmful by BrowserUk (Patriarch) on Jul 18, 2004 at 06:39 UTC
For p6, they already moved one step ahead with separation of `$thing x $count` being a scalar-repeat() and `$thing xx $count` being a list-repeat(). * My terms, probably incorrect. Looking at the output from `-MO=concise` for various uses of `x`, it looks like the optree has enough information in it to allow the repeat operator (or maybe the peep-hole optimiser) to determine whether the list being repeated contains a single 'active' element. Where 'active' is basically anything that isn't a constant or simple scalar: an srefgen; a function call etc. and have a special case for calling that active element iterator wise. The problem is it would the require some way to indicate when you really did want the list-wise replication of a single actively generated list item, and would break all existing uses. So, I guess the question is: Is there any syntactically nice way of indicating the difference between `my @data = rand xx 1000;` meaning I want a thousand different random numbers and `my @data = rand xx 1000;` I want a thousand copies of the same random number. I toyed with `my @data = rand xxx 1000;` for the former, but that would probably get every site displaying perl code using it blocked under "18 USC 2257", which might not be a good idea :) Another possibility is that `my @a = { ... } xx 1000;` would call the anon. block (or subref) 1000 times, but whether that is sufficiently clearer than `my @a = map{ ... } 1 .. 1000;` to be worth the cruft is the kind of decision that LW gets right whilst the rest of us are still uming annd ahhing. Examine what is said, not who speaks. "Efficiency is intelligent laziness." -David Dunham "Think for yourself!" - Abigail "Memory, processor, disk in that order on the hardware side. Algorithm, algoritm, algorithm on the code side." - tachyon	[reply] [d/l] [select]
Re^3: Using x to build data structures considered harmful by ihb (Deacon) on Jul 18, 2004 at 11:09 UTC
I was thinking that "hey, what's wrong with `map`" but then I reread your code and found an answer: you are producing a list of 1 000 001 elements. Having an operator that just uses a count operand instead of a range with equally many elements can indeed have its use. Though, I think introducing another operator or somesuch that would be a "reevaluating `x` operator" would border to operator bloating (as we have `map` which isn't unreadable if you know `map`). That could be said about a lot of the features and operators we love in Perl today (e.g. `for (LIST)` compared to C-style `for (;;)`), so I shouldn't say too much. But just because "we" are designing a language almost from scratch doesn't mean we should tuck in every feature we want. I think cleanlyness is good in a language, but so is DWIM and adaption for common tasks. These and other factors should be weighted against each other or we might end up with any of the extremes we dislike today. But of course, it's always good to ponder and discuss issues like this if the question isn't "how should we tuck it in" but rather "does this provide real value and how would it fit". Just my thought, `ihb`	[reply] [d/l] [select]