Hi guys, As a newby to haskell, I was curious, what is the best way to splice an array or do things in the middle? For example, binary search requires i do in sudocode define binary search array target. Find middle element. If target is middle element then return target else if target < middle element then binary search array[0:target] else binary search array[target:end] How can I get this splicing with haskell? I can't just use head here. I can't do array!!n: where n is some number. Thanks, Derek
You can use the various splitAts in Data.List, Data.Vector to split a list
at an index. You can also use drop and take to get a splice ie. drop 4
(take 2) is a splice from 3:5.
On Sat, Jun 13, 2015 at 9:36 AM, derek riemer
Hi guys, As a newby to haskell, I was curious, what is the best way to splice an array or do things in the middle? For example, binary search requires i do in sudocode define binary search array target. Find middle element. If target is middle element then return target else if target < middle element then binary search array[0:target] else binary search array[target:end]
How can I get this splicing with haskell? I can't just use head here. I can't do array!!n: where n is some number.
Thanks, Derek _______________________________________________ Beginners mailing list Beginners@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
Hi, I don't see anything as a Prelude function, but you can do something with a combination of take and drop: rangeOf:: Int -> Int -> [a] rangeOf x y = take y . drop x rangeOf 2 4 [1 .. 5] -- [3,4,5] I have not included any bounds check. It's up to you. For added benefits, look up dropWhile and takeWhile. HTH. Hi guys, As a newby to haskell, I was curious, what is the best way to splice an array or do things in the middle? For example, binary search requires i do in sudocode define binary search array target. Find middle element. If target is middle element then return target else if target < middle element then binary search array[0:target] else binary search array[target:end] How can I get this splicing with haskell? I can't just use head here. I can't do array!!n: where n is some number. Thanks, Derek _______________________________________________ Beginners mailing list Beginners@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
On 06/13/2015 09:36 AM, derek riemer wrote:
Hi guys, As a newby to haskell, I was curious, what is the best way to splice an array or do things in the middle?
If you REALLY want to slice and aren't worried about index-safety, you should try using vectors instead of plain lists: https://hackage.haskell.org/package/vector/docs/Data-Vector.html On the right side of that page there's an index; you want the section called "Extracting subvectors (slicing)." You will need to install the "vector" package to get that stuff.
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