F# for heating

[|1..999|] |> Array.Parallel.iter (fun _ ->
    while true do ignore())

8 thoughts on “F# for heating”

1. Pingback: F# Weekly #51, 2012 « Sergey Tihon's Blog
2. this is really cool 🙂

   Reply
3. Can you help to write efficient code in F# to achieve following.
   — connect to database and get dataset
   — prepare my object (i.e Person(){firstname, lastname) from this data and create a List of Person object.

   — Now whenever I need to access person details i read it from this collection. No more calls to database

   In My code i have achieved to do all of them except the last point. Every time i access Person object its going to database and reload the data 😦

   thanks in advance. is there any personal email address from you so i can contact you about some of the implementation in F# i am working on

   many thanks in advance 🙂

   Reply
   1. It is really depend on the database that you use. If you use SQL for example, you should use SqlTypeProvider. If you use Mongo, then Fsharp.Mongo will be good choice. Please share a bit more details.
      BTW. StackOverflow http://stackoverflow.com/questions/tagged/f%23 is great place for questions, there are lot of experts there.

      Reply
4. Reblogged this on D Says and commented:
   This is a real fun and let your frustration go out from your computer.

   Reply
5. thanks for the reply . Here is my code below.
   module sql
   open System
   open System.Collections.Generic
   open System.Data
   open System.Data.SqlClient
   open System.Reflection
   open System.Data.OleDb;
   open System.Text.RegularExpressions
   open Microsoft.FSharp.Reflection

   // Using records to store the data
   type Person = { FirstName:string; LastName:string; Age:int }

   let connectionString= “myDBConnectionstring”
   // Runs the specified query ‘sql’ and formats rows using function ‘f’
   let query sql f =

   seq { use cn = new SqlConnection(connectionString) // will be disposed
   let da = new SqlDataAdapter(new SqlCommand(sql, cn))
   let ds = new DataSet()
   cn.Open()
   let i = da.Fill(ds)
   let rowCol = ds.Tables.[0].Rows
   for i in 0 .. (10 – 1) do // just take 10 records for test
   yield f (rowCol.[i]) }

   let names = query “SELECT * FROM User_tbl” (fun row -> row.[“FirstName”])
   for name in names do printfn “%A” name

   names |> Seq.iter (printfn “%A”)

   Now when i access objects from “names” than its accessing the database (which i understand why as my code is written like this )
   i want to load it once only.

   Reply
   1. It is happened because the sequence is lazy. Please try to load it into list or array, like this
      let names = query “SELECT * FROM User_tbl” (fun row -> row.[“FirstName”]) |> Seq.toArray

      But, much shorter code will be with TypeProviders
      http://msdn.microsoft.com/en-us/library/hh361033.aspx

      Reply
6. Hello
   Is there something called Eval or similiar function available in F# ? i have already looked on community but could not really get a clear direction.
   Here is what i want to achieve

   type Parameter = { Paramkey:string; ParamFormula:string; ParamDefaultValue:int }

   let p1 = { Paramkey = “p1”; ParamFormula = “10”; ParamDefaultValue = 10; }
   let p2 = { Paramkey = “p2”; ParamFormula = “p1*2”; ParamDefaultValue = 20; }
   let p3 = { Paramkey = “p3”; ParamFormula = “10+(p1*3*p2)”; ParamDefaultValue = 30; }

   let ParameterList = [p1;p2;p3]
   let Formula1 = p1.ParamFormula + p2.ParamFormula +p3.ParamFormula

   let Formula2 = Formula1*10

   call Formula2

   the parameter formulas will be coming straight from some datastore .

   Reply