Types & Values

The Carina DSL is a statically-aware language with the following value types.

Primitive Types

String

Strings are enclosed in double quotes:

let name = 'my-vpc'
let region = 'ap-northeast-1'

Escape Sequences

Strings support the following escape sequences:

Sequence	Meaning
\"	Double quote
\\	Backslash
\n	Newline
\r	Carriage return
\t	Tab
\$	Literal dollar sign (prevents interpolation)

String Interpolation

Embed expressions inside strings with ${}:

let env = 'prod'
let name = "vpc-${env}"           # => 'vpc-prod'
let cidr = "${base_cidr}"         # => value of base_cidr
let tag = "${env}-${service}"     # => 'prod-web'

Any expression can appear inside ${}, including function calls:

let tag = "vpc-${join("-", ["prod", "web"])}"

Int

Integer values, optionally negative:

let port = 443
let offset = -1
let count = 0

Float

Floating-point values with a decimal point:

let ratio = 0.5
let threshold = -3.14

Bool

Boolean values true or false:

let enabled = true
let public = false

Collection Types

List

Ordered sequences enclosed in square brackets:

let zones = ['ap-northeast-1a', 'ap-northeast-1c', 'ap-northeast-1d']
let ports = [80, 443, 8080]
let empty = []

Lists can contain mixed types and a trailing comma is allowed:

let mixed = [
  'hello',
  42,
  true,
]

Map

Key-value collections enclosed in curly braces. Keys are identifiers (unquoted), values are expressions:

let config = {
  dev = '10.0.0.0/16'
  stg = '10.1.0.0/16'
}

Maps are also used for resource tags and nested configuration:

awscc.ec2.vpc {
  cidr_block = '10.0.0.0/16'

  tags = {
    Name        = 'main'
    Environment = 'prod'
  }
}

Namespaced Identifiers

Dot-separated identifiers are used for resource types and enum values. They are not strings and are not quoted.

Resource Types

Resource types use the format provider.service.resource_type:

awscc.ec2.vpc { ... }
awscc.ec2.subnet { ... }
awscc.s3.bucket { ... }

Enum Identifiers

Enum values are namespaced identifiers that represent predefined constants:

# Provider-level enums
awscc.Region.ap_northeast_1
aws.Region.us_east_1

# Resource-level enums
awscc.ec2.vpc.InstanceTenancy.default

Enum identifiers are used directly as attribute values without quotes:

provider awscc {
  region = awscc.Region.ap_northeast_1
}

awscc.ec2.vpc {
  instance_tenancy = awscc.ec2.vpc.InstanceTenancy.default
}

Resource References

When a resource is bound with let, its attributes can be accessed using dot notation:

let vpc = awscc.ec2.vpc {
  cidr_block = '10.0.0.0/16'
}

let subnet = awscc.ec2.subnet {
  vpc_id     = vpc.vpc_id      # Reference vpc's vpc_id attribute
  cidr_block = '10.0.1.0/24'
}

Chained Access

Dot notation can be chained for nested access:

let sg = network.security_group.group_id

Index Access

Use square brackets to access list elements or map values:

let first_zone = zones[0]
let dev_cidr = config['dev']

Index and field access can be combined:

let subnet_id = subnets[0].subnet_id

Type Expressions

Type expressions are used in arguments and attributes blocks in modules, and in function parameters.

Simple Types

arguments {
  name      : string
  count     : int
  ratio     : float
  enabled   : bool
  cidr_block: cidr
  role_arn  : arn
}

Generic Types

list and map accept a type parameter:

arguments {
  subnet_ids  : list(string)
  cidr_blocks : list(cidr)
  tags        : map(string)
}

Resource Type References

Resource types can be used as type expressions to indicate a reference:

attributes {
  vpc_id   : awscc.ec2.vpc = vpc.vpc_id
  subnet_id: awscc.ec2.subnet = subnet.subnet_id
}

Null

The null literal represents the absence of a value. It can only appear in validate expressions such as require statements and argument validation:

require value != null, 'Value must not be null'