F# Discriminated Unions Basic Discriminated Union Usage
Example
Discriminated unions in F# offer a a way to define types which may hold any number of different data types. Their functionality is similar to C++ unions or VB variants, but with the additional benefit of being type safe.
// define a discriminated union that can hold either a float or a string
type numOrString =
| F of float
| S of string
let str = S "hi" // use the S constructor to create a string
let fl = F 3.5 // use the F constructor to create a float
// you can use pattern matching to deconstruct each type
let whatType x =
match x with
| F f -> printfn "%f is a float" f
| S s -> printfn "%s is a string" s
whatType str // hi is a string
whatType fl // 3.500000 is a float
