Derivatives of a polynomial in F#
October 8, 2011 § Leave a Comment
Just because I was bored…
type Term = {Coefficient: int; Power: int}
type Term = {Coefficient: int; Power: int}
type Polynomial = list<Term>
let derivative polynomial =
polynomial |> List.map (fun term -> {Coefficient = term.Coefficient * term.Power; Power = term.Power - 1}) |> List.filter (fun x -> x.Power >= 0)
let prettyPrint polynomial =
let sortedTerms = polynomial |> List.sortBy (fun term -> -term.Power)
let rec printTerms terms =
match terms with
| [] -> ""
| [term] ->
match term.Power with
| 0 -> sprintf "%d" term.Coefficient
| 1 -> sprintf "%dx" term.Coefficient
| n -> sprintf "%dx^%d" term.Coefficient term.Power
| h::t -> printTerms [h] + " + " + printTerms t
printTerms sortedTerms
let sample = [{Coefficient=3; Power=2};{Coefficient=5; Power=1};{Coefficient=4;Power=0}]
let derived = sample |> derivative
printfn "Polynomial:\t%s" <| prettyPrint sample
printfn "Derivative:\t%s" <| prettyPrint derived
