PPrint is a pretty printing combinator library for text documents that can be rendered to a desired maximum width.
Docs
Background
Example
Here is an example of how one could define a function with signature
module Json =
val pretty: JsonValue -> Docfor pretty printing JSON values:
open System.Json
open PPrint
let inline (^) x = x
module Json =
let private prettySeq (l, r) toDoc xs =
if Seq.isEmpty xs
then l <^> r
else let ds = xs |> Seq.map toDoc |> punctuate comma |> vsep
l <..> ds |> nest 2 <..> r |> group
let rec pretty (json: JsonValue) =
match json with
| :? JsonObject as json ->
json
|> prettySeq lrbrace ^ fun kv ->
pretty ^ JsonPrimitive kv.Key <^> colon <+> pretty kv.Value
| :? JsonArray as json ->
json
|> prettySeq lrbracket pretty
| null ->
txt "null"
| _ ->
json
|> string
|> txtGiven a JSON value
let json = JsonValue.Parse """
{
"firstName": "John",
"lastName": "Smith",
"isAlive": true,
"age": 25,
"address": {
"streetAddress": "21 2nd Street",
"city": "New York",
"state": "NY",
"postalCode": "10021-3100"
},
"phoneNumbers": [
{
"type": "home",
"number": "212 555-1234"
},
{
"type": "office",
"number": "646 555-4567"
}
],
"children": [],
"spouse": null
}
"""we can render it to different desired maximum widths. For example,
json |> Json.pretty |> println ^ Some 40produces
{
"address": {
"city": "New York",
"postalCode": "10021-3100",
"state": "NY",
"streetAddress": "21 2nd Street"
},
"age": 25,
"children": [],
"firstName": "John",
"isAlive": true,
"lastName": "Smith",
"phoneNumbers": [
{
"number": "212 555-1234",
"type": "home"
},
{
"number": "646 555-4567",
"type": "office"
}
],
"spouse": null
}
and
json |> Json.pretty |> println ^ Some 80produces
{
"address": {
"city": "New York",
"postalCode": "10021-3100",
"state": "NY",
"streetAddress": "21 2nd Street"
},
"age": 25,
"children": [],
"firstName": "John",
"isAlive": true,
"lastName": "Smith",
"phoneNumbers": [
{"number": "212 555-1234", "type": "home"},
{"number": "646 555-4567", "type": "office"}
],
"spouse": null
}
