.NET Core 2.0 By Example

Variable declaration

F# uses the let keyword for the declaration of a variable, for example:

let square x = x*x

The compiler automatically detects this as a value type. If we pass a float value, the compiler will be able to understand that without declaring a data type. Variables in F# are immutable, so once a value is assigned to a variable, it can't be changed. They are compiled as static read-only properties.

The following example demonstrates this:

let x:int32 = 50let y:int32 = 30let z:int32 = x + y

Variables x, y, and z are all of type int32 and are immutable, meaning their value cannot be changed.

Let's print their values. The syntax is as follows:

printfn "x: %i" xprintfn "y: %i" yprintfn "z: %i" z

After the preceding code executes, ...