Prime decomposition: Difference between revisions

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+module Main exposing (main)
-{{task|Prime Numbers}}
+import Html exposing (Html, div, h1, text)
+import Html.Attributes exposing (style)
+-- See live:
+-- <nowiki>https://ellie-app.com/pMYxVPQ4fvca1</nowiki>
+accumulator : List Int
+accumulator =
+    []
+ts =
+    showFactors compositeNr 2 accumulator
+--compositeNr = 84894624407 -- ==> 3067 4357 6353
+-- compositeNr = 65536 -- = 2^16
+compositeNr = 2*3*5*7*11*13*17 -- = 510510
+main =
+        div
+            [ style "margin" "5%"
+            , style "font-size" "1.5em"
+            , style "color" "blue"
+            ]
+            [ h1 [] [ text "Prime Factorizer" ]
+            , text
+                ("Prime factors: "
+                    ++ listAsString ts
+                    ++ " from number "
+                    ++ String.fromInt (List.product ts)
+                )
+            ]
+showFactors : Int -> Int -> List Int -> List Int
+showFactors number factor acc =
+    if number < 2 then
+        acc
+        -- returns the final result if number < 2
+    else if
+        modBy factor number == 0
+        -- modulo used to get prime factors
+then let
+            v2 : List Int
+            v2 =
+                factor :: acc
+            number2 : Int
+            number2 =
+                number // factor
+        in
+        showFactors number2 factor v2
+        -- recursive call
+        -- this modulus function is used
+        -- in order to output factor !=2
+    else
+        let
+            factor2 : Int
+            factor2 =
+                factor + 1
+        in
+        showFactors number factor2 acc
+listAsString : List Int -> String
+listAsString myList =
+    List.map String.fromInt myList
+        |> List.map (\el -> " " ++ el)
+        |> List.foldl (++) " "
+-- Driver program to test above function
+-- compositeNr = 84894624407
+--      result = 3067 4357 6353{{task|Prime Numbers}}
 [[Category:Arbitrary precision]]
+<nowiki>==Elm==</nowiki>
-{{omit from|GUISS}}
+<nowiki><syntaxhighlight lang=”elm"></nowiki>{{omit from|GUISS}}
 The prime decomposition of a number is defined as a list of prime numbers