F# Reference Cells

Reference cells refer to memory locations. It allows you to create mutable values. F# uses immutable data structure by default.

You can create reference cells by using ref operator. It holds actual value.

Reference cells can be dereferenced by using! (Bang) operator. It uses : = operator to assign new value.

Syntax:

F# Reference Cells Example

let refVariable = ref 50
printf "%d" refVariable.Value

Output:

F# Reference Cells Example2

let refVariable22 = ref 50
printf "%d" refVariable.Value

refVariable22 := 100  			// Value has changed because it is mutable.

printf "\n%d" refVariable22.Value  

Output:

50
100

F# Reference Cells Value Property and Contents Field Example

let refVariable = ref 50

// modifying value by using Value property and <- operator
refVariable.Value <- 101
printf "\n%d" refVariable.Value            

// modifying value by using contents field and <- operator
refVariable.contents <- 102
printf "\n%d" refVariable.contents

Output:

101
102

F# Reference Cells vs. Mutable Variables

Reference cells and mutable variables both can be used in all situations except that compiler does not allow to use mutable variables in lambda expressions, sequence expressions etc. In such scenario, you can use reference cells.

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