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Indentation and Layout

FScript is indentation-aware: layout determines block structure.

This page shows the supported indentation styles you can use confidently.

1) Block indentation​

After let, if, for, match, and fun, increasing indentation opens a block. Dedenting closes it.

let describe n =
  if n > 0 then
    "positive"
  else
    "zero-or-negative"

2) Function declaration styles​

Single-line parameters​

let add x y = x + y

Multi-line parameters (aligned)​

Continuation parameter lines must start at the same column.

let formatAddress (address: {| City: string; Zip: int |})
                  (name: string) =
  $"{address.City} ({name})"

3) Pipeline with multiline lambda​

A lambda body can be placed on the next indented line inside call arguments.

let result =
  [0..9]
  |> List.map (fun i ->
      i + 1)
  |> List.filter (fun i -> i % 2 == 0)

4) match case alignment​

Case lines in a multiline match must align with each other.

let label value =
  match value with
  | Some x -> $"some:{x}"
  | None -> "none"

5) Record and map literal layout styles​

Single-line record and map​

let person = { Name = "Ada"; Age = 37 }
let ports = { ["http"] = 80; ["https"] = 443 }

Compact multiline record and map​

Opening { stays on the line of the first field/entry. Closing } stays on the line of the last field/entry.

let person = { Name = "Ada"
               Age = 37 }

let ports = { ["http"] = 80
              ["https"] = 443 }

6) List layout styles​

Single-line list​

let xs = [1; 2; 3]

Compact multiline list​

let xs = [1
          2
          3]

For non-empty lists, do not put [ or ] on standalone lines.

7) Union declaration styles​

Single-line union​

type Shape = | Point | Circle of int

Multiline union​

type Shape =
  | Point
  | Circle of int

8) Common invalid layout patterns​

Misaligned multiline parameters​

// Invalid style: second parameter line is not aligned
let f (x: int)
    (y: int) = x + y

Block delimiter style for non-empty list/map​

// Invalid style
let xs =
  [
    1
    2
  ]

Use compact list/map/record multiline styles instead.