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"be consistent"

emulate Python's range function

by jeffa (Bishop)
on May 08, 2003 at 15:13 UTC ( [id://256552]=CUFP: print w/replies, xml ) Need Help??

A long time ago, i suggested a rather drawn out way to transform a 1-D array into a 2-D array: (jeffa) Re: Structure for nested html::template loops. It uses autovivification to know which row to add the current piece of data to. Upon showing this to one of my college professors, he showed me a much simpler way to achieve the same results in Python, using the range built-in function.

That function takes 3 args, the first two are the start and stop points ... and if we stop right there then this function is complete "word-candy", as the dot dot operator already does this. But, the 3rd argument is the 'step', which allows for some cool stuff:

use Data::Dumper; my $step = 5; my @array = ('a'..'z'); print Dumper [ map[ @array[$_..$_+$step-1] ], range(0,$#array,$step) ];
This allows you to create a 2-D array from a 1-D array, 'folded' where ever you like. At the end, if there are no more element to stuff in the last row, the correct amount of 'undef' values will be pushed.

Now all we need is the ability to handle 'lazy lists' like Python's xrange. ;)

(and a big thanks to merlyn for reviewing this and improving it)

UPDATE: ack ... rob_au already posted something similar: Stepping through an array. (he also points out Abigail-II's solution - no grep needed!)

# usage: my @AoA = range($start,$stop[,$step]); sub range {grep!(($_-$_[0])%($_[2]||1)),$_[0]..$_[1]}

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