F# Type Annotation

F# allows type annotation. By using type annotation you can explicitly mention the type of identifier, parameter, return value of a function. You must use: (colon) to apply annotation in F#.

Let’s see where and how we can apply type annotation.

• Type annotation in variable (identifier)
• Type annotation in function parameter and return type

F# Type Annotation in variable (identifier) Example

Here, we are explicitly mentioning type of variable followed by: (colon).

Output:

10  

F# Type Annotation in Function Example

Here, we are using type annotation in parameters and return value.

Output:

30