Re^3: Concise foreach expression

> Could you explain what you mean there?

I was talking about chaining maps or fors to simulate nested foreach loops.

I.o.w. list comprehensions are very hard to implement in Perl without nested blocks.

e.g. try to implement this Python example for "Pythagorean triples" w/o nesting

>>> [(x,y,z) for x in range(1,30) for y in range(x,30) for z in range(
+y,30) if x**2 + y**2 == z**2]

[(3, 4, 5), (5, 12, 13), (6, 8, 10), (7, 24, 25), (8, 15, 17), (9, 12,
+ 15), (10, 24, 26), (12, 16, 20), (15, 20, 25), (20, 21, 29)]
[download]

Cheers Rolf

_{(addicted to the Perl Programming Language and ☆☆☆☆ :)}

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Re^4: Concise foreach expression by AppleFritter (Vicar) on Aug 29, 2014 at 17:21 UTC
Ah, yes, I see what you mean.	[reply]
Re^5: Concise foreach expression by LanX (Saint) on Aug 29, 2014 at 17:42 UTC
FWIW I once implemented a ( Monad style ;-) approach to emulate this `@results = take { [$a,$b,$c] if $a2 +$b2 ==$c2 } from {1..30} $a from {1..$a} $b from {1...$b} $c` `take(&$)` and `from(&$$)` where just ordinary functions passing iterators around. The problem I couldn't solve was a DRY scoping of the variables, to be strict I needed to surround the whole expression with `{ my($a,$b,$c); ... }` [download] `my` declarations don't effect the scope of the same line. :( Cheers Rolf _{(addicted to the Perl Programming Language and ☆☆☆☆ :)} update hmm maybe this syntax is acceptable? ~~`from { 1..30} my $a from {1..$a} my $b from { 1...$b} my $c; @results = take { [$a,$b,$c] if $a2 +$b2 ==$c2 }`~~ ~~[download]~~ ~~when called from void context `from()` could put the iterator into `$_` , and `take()` could read it again from `$_` if called with just one block arg...~~ never mind doesn't work.	[reply] [d/l] [select]

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