One of our restaurant clients wants to know which pizza topping combinations are the most popular. Write a throw-away .NET console application that will download orders directly from http://files.olo.com/pizzas.json and output the top 20 most frequently ordered pizza topping combinations. List the toppings for each popular pizza topping combinat…

Olo.fs

open FSharp.Data

type Pizza = JsonProvider<"pizzas.json">

type ToppingFrequencyPair = { Toppings: string[]; Frequency: int }

let getToppingFrequencyPair grouping =
    { Toppings = fst grouping; Frequency = snd grouping |> Array.length }

[<EntryPoint>]
let main argv =
    let bestToppings = 
        Pizza.Load "http://files.olo.com/pizzas.json"
        |> Array.groupBy (fun x -> x.Toppings |> Array.sort)
        |> Array.map getToppingFrequencyPair
        |> Array.sortByDescending (fun x -> x.Frequency)
        |> Array.take 20

    bestToppings |> Array.map (fun x -> printfn "%A" x) |> ignore
    0 // return an integer exit code

Olo.fsproj

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>netcoreapp2.1</TargetFramework>
  </PropertyGroup>

  <ItemGroup>
    <Compile Include="Program.fs" />
  </ItemGroup>

  <ItemGroup>
      <PackageReference Include="FSharp.Data" Version="3.0.0" />
  </ItemGroup>

</Project>

{Toppings = [|"pepperoni"|];
 Frequency = 4616;}
{Toppings = [|"mozzarella cheese"|];
 Frequency = 1014;}
{Toppings = [|"four cheese"|];
 Frequency = 956;}
{Toppings = [|"bacon"|];
 Frequency = 732;}
{Toppings = [|"beef"|];
 Frequency = 623;}
{Toppings = [|"sausage"|];
 Frequency = 402;}
{Toppings = [|"italian sausage"|];
 Frequency = 361;}
{Toppings = [|"chicken"|];
 Frequency = 229;}
{Toppings = [|"four cheese"; "pepperoni"|];
 Frequency = 203;}
{Toppings = [|"ham"|];
 Frequency = 165;}
{Toppings = [|"mushrooms"|];
 Frequency = 159;}
{Toppings = [|"mozzarella cheese"; "pepperoni"|];
 Frequency = 155;}
{Toppings = [|"beef"; "pepperoni"|];
 Frequency = 122;}
{Toppings = [|"bacon"; "pepperoni"|];
 Frequency = 121;}
{Toppings = [|"black olives"|];
 Frequency = 117;}
{Toppings = [|"alredo sauce"|];
 Frequency = 101;}
{Toppings = [|"pepperoni"; "sausage"|];
 Frequency = 96;}
{Toppings = [|"cheddar cheese"|];
 Frequency = 95;}
{Toppings = [|"italian sausage"; "pepperoni"|];
 Frequency = 85;}
{Toppings = [|"pineapple"|];
 Frequency = 79;}