[Haskell-cafe] How to use roots package?

James Cook mokus at deepbondi.net
Thu Mar 24 01:49:16 CET 2011

On Mar 23, 2011, at 6:57 PM, Henning Thielemann wrote:

> James Cook schrieb:
>> Those are both options,  as is to simply restart findRoot if it  
>> returns
>> a 'Left' vaule.  I personally would incline toward a custom driver
>> function (findRoot).  I should probably add one to the library that
>> accepts a step limit and/or one that just iterates until convergence.
> I thought that the mosts Haskellish way to do numerical iterations  
> is to
> generate a list of successive approximations (by List.iterate, of
> course) and then let the user choose where and why he wants to abort  
> the
> list, and thus the iteration.

That's probably true, and the same module exports a function that does  
so.  But sometimes you just want to ask "what is the root?", and get  
an answer without taking (possibly literally) forever.

Overall, the code is relatively un-Haskellish to begin with though.   
It was assembled in a short period of time in order to simply have  
code that performs the task, and hasn't really been touched since.

-- James
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