Range Operator

The range operator .. is used to declare lists of ordered sequence values.

Using the range operator, we can quickly create a list of ordered sequence values with a single line of code. For instance, the following F# code creates a list of integers ranging from 1 to 5:

[1..5]
// Output: [1; 2; 3; 4; 5]

Similarly, we can create a list of characters ranging from ‘a’ to ‘f’:

['a'..'f']
// Output: ['a'; 'b'; 'c'; 'd'; 'e'; 'f']

By default, the range operator creates a list with an increment of 1. However, we can change the increment by specifying a step value. For instance, to create a list of integers ranging from 1 to 10 with an increment of 2, we can use the following code:

[1..2..10]
// Output: [1; 3; 5; 7; 9]

Here, the 2 in 1..2..10 specifies that we want the range to increment by 2 instead of the default of 1.

The range operator can also be used to create a list in reverse order. To create a list of integers ranging from 10 to 0 in reverse order, we can use the following code:

[10..-1..0];;
// Output: [10; 9; 8; 7; 6; 5; 4; 3; 2; 1; 0]

Here, the -1 in 10..-1..0 specifies that we want the range to increment by -1, which effectively creates a reversed list.