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The Orion syntax is implemented with HCL from Hashicorp. If you worked with Nomad or Terraform you are used to working with this type of syntax.

The below context has been extracted from HCL README

For a complete grammar, please see the parser itself. A high-level overview of the syntax and grammar is listed here.

  • Single line comments start with # or //

  • Multi-line comments are wrapped in /* and */. Nested block comments are not allowed. A multi-line comment (also known as a block comment) terminates at the first */ found.

  • Values are assigned with the syntax key = value (whitespace doesn’t matter). The value can be any primitive: a string, number, boolean, object, or list.

  • Strings are double-quoted and can contain any UTF-8 characters. Example: "Hello, World"

  • Multi-line strings start with <<EOF at the end of a line, and end with EOF on its own line (here documents). Any text may be used in place of EOF. Example:
  • Numbers are assumed to be base 10. If you prefix a number with 0x, it is treated as a hexadecimal. If it is prefixed with 0, it is treated as an octal. Numbers can be in scientific notation: “1e10”.

  • Boolean values: true, false

  • Arrays can be made by wrapping it in []. Example: ["foo", "bar", 42]. Arrays can contain primitives, other arrays, and objects. As an alternative, lists of objects can be created with repeated blocks, using this structure:

    service {
        key = "value"
    service {
        key = "value"

Objects and nested objects are created using the structure shown below:

variable "ami" {
    description = "the AMI to use"

This would be equivalent to the following json:

  "variable": {
      "ami": {
          "description": "the AMI to use"