Pkl cheatsheet

// This is a comment

/* This is a multi-line
   multi-line comment
*/
/// User-facing documentation for a member

module MyModule

name = "Dodo" // Immutable by default
local age = 42 // Local scope
var mutableValue = 10 // Mutable (use sparingly)

dodo {
  name = "Dodo"
  extinct = true
}
// Access: dodo.name

dodo {
  name = "Dodo"
  extinct = true
}

revived = (dodo) {
  extinct = false
}

// Integer
num = 123
hex = 0x1A
binary = 0b1011
octal = 0o755

// Float
float = 1.23
scientific = 1.2e-3

// Readable
large = 1_000_000.50

isActive = true
isFalse = false

text = "Hello, Pkl!"
unicode = "\u{1F426}" // 🐦
multiline = """
Line 1
Line 2
"""

time = 5.min
delay = 300.ms

size = 5.mb
large = 1.gb

nothing = null

// List
numbers = [1, 2, 3]

// Listing (lazy evaluated)
foods = new Listing<String> {
  "bacon"
  "nachos"
}

// Set
unique = new Set {
  1
  2
  3
}

// Mapping
pairs = new Mapping {
  ["key1"] = "value1"
  ["key2"] = "value2"
}

class Bird {
  name: String
  extinct: Boolean
}

dodo = new Bird { name = "Dodo"; extinct = true }

age: Int(isBetween(0, 130))
oddName: String(length.isOdd, chars.first == chars.last)

status = if (age > 18) "Adult" else "Minor"

// Generate over a list
names = List("Pigeon", "Barn owl", "Parrot")

birds {
  for (_name in names) {
    new {
      name = _name
      lifespan = 42
    }
  }
}

// Generate over a map
namesAndLifespans = Map("Pigeon", 8, "Barn owl", 15, "Parrot", 20)

birdsByName {
  for (_name, _lifespan in namesAndLifespans) {
    [_name] {
      name = _name
      lifespan = _lifespan
    }
  }
}

needNfs = true
class Server {
  type: String
  name: String
}

servers {
  when (needNfs) {
    new Server {
      type = "NFS"
      name = "nfs-server"
    }
  }
  new Server {
    type = "WWW"
    name = "www-server"
  }
  new Server {
    type = "App"
    name = "app-server"
  }
}

result = let (x = 5) x * 2

function double(x: Int): Int = x * 2

class Bird {
    function describe() = "\(name) is \(extinct ? "extinct" : "alive")"
}

doubled = double(5) // 10
desc = dodo.describe()

throw("Invalid input")

age: Int(isPositive) // Throws if negative