# Difference between revisions of "Add polynomials"

From HaskellWiki

(Numeric Prelude) |
m (Remove the incomplete multiply function) |
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Line 26: | Line 26: | ||

addManyPolys :: [Poly] -> Poly |
addManyPolys :: [Poly] -> Poly |
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addManyPolys ps = foldl 0 addPoly ps |
addManyPolys ps = foldl 0 addPoly ps |
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− | |||

− | multiply :: [Int] -> [Int] -> [Int] |
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− | --multiply polynomials together. |
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− | multiply [] ys = ys |
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− | multiply xs [] = xs |
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− | multiply ((a,b):xs) ((c,d):ys) |
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− | |||

main = do |
main = do |

## Latest revision as of 05:07, 3 May 2009

Polynomial Algebra

```
#!/usr/local/bin/runhugs
module Main where
type Poly = [(Int,Int)]
-- assume sorted by increasing exponent.
-- data Rational = (Poly, Poly)
-- an interesting thing to observe:
-- when adding, the null polynomial is zero.
-- when multiplying it is one. This concept emerges implicitly
-- in these definitions.
addPoly :: Poly -> Poly -> Poly
addPoly [] ys = ys
addPoly xs [] = xs
addPoly ((a,b):xs) ((c,d):ys)
| a == c = ((a,b+d):(addPoly xs ys))
| a < c = ((a,b):(addPoly xs ((c,d):ys)))
| a > c = ((c,d):(addPoly ((a,b):xs) ys))
addManyPolys :: [Poly] -> Poly
addManyPolys ps = foldl 0 addPoly ps
main = do
putStr $ show $ addPoly [(0,1),(2,1)] [(0,1)]
```

## See also

- Numeric Prelude [1]
- HTam [2]