https://wiki.haskell.org/index.php?title=Haskell_Quiz/Internal_Rate_of_Return/Solution_Dolio&feed=atom&action=history
Haskell Quiz/Internal Rate of Return/Solution Dolio - Revision history
2024-03-19T07:36:26Z
Revision history for this page on the wiki
MediaWiki 1.35.5
https://wiki.haskell.org/index.php?title=Haskell_Quiz/Internal_Rate_of_Return/Solution_Dolio&diff=18983&oldid=prev
Dolio: use until instead of iterate
2008-02-09T13:41:12Z
<p>use until instead of iterate</p>
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 13:41, 9 February 2008</td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>secant f delta = fst <del class="diffchange diffchange-inline">.</del> <del class="diffchange diffchange-inline">head . dropWhile</del> err<del class="diffchange diffchange-inline"> . iterate</del> update<del class="diffchange diffchange-inline"> $</del> (0,1)</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>secant f delta = fst <ins class="diffchange diffchange-inline">$</ins> <ins class="diffchange diffchange-inline">until</ins> err update (0,1)</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div> where</div></td>
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Dolio
https://wiki.haskell.org/index.php?title=Haskell_Quiz/Internal_Rate_of_Return/Solution_Dolio&diff=18978&oldid=prev
Dolio: category
2008-02-09T12:41:59Z
<p>category</p>
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 12:41, 9 February 2008</td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>My solution for this quiz uses the [http://en.wikipedia.org/wiki/Secant_method secant method], which is quite easy to implement.</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>My solution for this quiz uses the [http://en.wikipedia.org/wiki/Secant_method secant method], which is quite easy to implement.</div></td>
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Dolio
https://wiki.haskell.org/index.php?title=Haskell_Quiz/Internal_Rate_of_Return/Solution_Dolio&diff=18977&oldid=prev
Dolio: creation
2008-02-09T12:40:40Z
<p>creation</p>
<p><b>New page</b></p><div>My solution for this quiz uses the [http://en.wikipedia.org/wiki/Secant_method secant method], which is quite easy to implement.<br />
<br />
<haskell><br />
import Data.Function<br />
import Numeric<br />
import System.Environment<br />
<br />
secant :: (Double -> Double) -> Double -> Double<br />
secant f delta = fst . head . dropWhile err . iterate update $ (0,1)<br />
where<br />
update (x,y) = (x - (x - y)*(f x)/(f x - f y), x)<br />
err (x,y) = abs (x - y) > delta<br />
<br />
npv :: Double -> [Double] -> Double<br />
npv i = sum . zipWith (\t c -> c / (1 + i)**t) [0..]<br />
<br />
main = do (s:t) <- getArgs<br />
let sig = read s<br />
cs = map read t<br />
putStrLn . ($"") . showFFloat (Just sig) $ secant (flip npv cs) (0.1^sig)<br />
</haskell><br />
<br />
The resulting program expects the first argument to be the number of digits to be displayed after the decimal point, while the rest are the yearly income. For instance:<br />
<br />
./IRR 4 -100 30 35 40 45<br />
0.1709</div>
Dolio