[Haskell-cafe] Bifold: a simultaneous foldr and foldl

Larry Evans cppljevans at suddenlink.net
Fri Dec 3 22:41:56 CET 2010

On 12/01/10 21:35, Larry Evans wrote:
> On 11/30/10 13:43, Noah Easterly wrote:
>> Thanks, Larry, this is some interesting stuff.
>> I'm not sure yet whether Q is equivalent - it may be, but I haven't been
>> able to thoroughly grok it yet.
> Hi Noah,
> The attached is my attempt at reproducing your code and also
> contains an alternative attempt at emulating the code in
> section 12.5 of:
>   http://www.thocp.net/biographies/papers/backus_turingaward_lecture.pdf
The attached code is a revision of my previous if_recur attempt
at emulated the section 12.5 code.  This revision added the i
function from the seciton 12.5 (instead of delegating that
task to the h function).  The 2nd attachment shows the output.
It shows that by modifying the args to if_recur, you can
reproduce the output from foldl or foldr.
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