a record is similar to a tuple, however it contains named fields. for example,

type website =
   { title : string;
     url : string }

defining record

a record is defined as a type using the type keyword, and the fields of the record are defined as a semicolon-separated list.

syntax for defining a record is −

type recordname =
   { [ fieldname : datatype ] + }

creating a record

you can create a record by specifying the record's fields. for example, let us create a website record named homepage −

let homepage = { title = "tutorialspoint"; url = "www.tutorialspoint.com" }

the following examples will explain the concepts −

example 1

this program defines a record type named website. then it creates some records of type website and prints the records.

(* defining a record type named website *)
type website =
   { title : string;
      url : string }

(* creating some records *)
let homepage = { title = "tutorialspoint"; url = "www.tutorialspoint.com" }
let cpage = { title = "learn c"; url = "www.tutorialspoint.com/cprogramming/index.htm" }
let fsharppage = { title = "learn f#"; url = "www.tutorialspoint.com/fsharp/index.htm" }
let csharppage = { title = "learn c#"; url = "www.tutorialspoint.com/csharp/index.htm" }

(*printing records *)
(printfn "home page: title: %a \n \t url: %a") homepage.title homepage.url
(printfn "c page: title: %a \n \t url: %a") cpage.title cpage.url
(printfn "f# page: title: %a \n \t url: %a") fsharppage.title fsharppage.url
(printfn "c# page: title: %a \n \t url: %a") csharppage.title csharppage.url

when you compile and execute the program, it yields the following output −

home page: title: "tutorialspoint"
       url: "www.tutorialspoint.com"
c page: title: "learn c"
      url: "www.tutorialspoint.com/cprogramming/index.htm"
f# page: title: "learn f#"
      url: "www.tutorialspoint.com/fsharp/index.htm"
c# page: title: "learn c#"
      url: "www.tutorialspoint.com/csharp/index.htm"

example 2

type student =
   { name : string;
      id : int;
      registrationtext : string;
      isregistered : bool }

let getstudent name id =
   { name = name; id = id; registrationtext = null; isregistered = false }

let registerstudent st =
   { st with
      registrationtext = "registered";
      isregistered = true }

let printstudent msg st =
   printfn "%s: %a" msg st

let main() =
   let preregisteredstudent = getstudent "zara" 10
   let postregisteredstudent = registerstudent preregisteredstudent

   printstudent "before registration: " preregisteredstudent
   printstudent "after registration: " postregisteredstudent

main()

when you compile and execute the program, it yields the following output −

before registration: : {name = "zara";
   id = 10;
   registrationtext = null;
   isregistered = false;}
after registration: : {name = "zara";
   id = 10;
   registrationtext = "registered";
   isregistered = true;}