yaml

The yaml module provides YAML parsing and stringification. It implements a line-based parser in pure Wren that supports common YAML features including nested structures, lists, and scalar types.

import "yaml" for Yaml

Yaml Class

Static Methods

Parses a YAML string and returns the corresponding Wren value.

• text (String) - YAML string to parse
• Returns: Parsed value (Map, List, String, Num, Bool, or null)

var data = Yaml.parse("name: Alice\nage: 30")
System.print(data["name"])  // Alice
System.print(data["age"])   // 30

var list = Yaml.parse("- one\n- two\n- three")
System.print(list[0])  // one

Converts a Wren value to a YAML string with default indentation (2 spaces).

• value (any) - Value to stringify
• Returns: YAML string

var yaml = Yaml.stringify({"name": "Alice", "age": 30})
System.print(yaml)
// name: Alice
// age: 30

Converts a Wren value to a YAML string with custom indentation.

• value (any) - Value to stringify
• indent (Num) - Number of spaces for indentation
• Returns: YAML string

var yaml = Yaml.stringify({"server": {"host": "localhost"}}, 4)
System.print(yaml)
// server:
//     host: localhost

Supported Features

Key-Value Pairs

var data = Yaml.parse("
name: Alice
age: 30
email: alice@example.com
")
System.print(data["name"])  // Alice

Nested Maps

var config = Yaml.parse("
database:
  host: localhost
  port: 5432
  credentials:
    user: admin
    password: secret
")
System.print(config["database"]["host"])  // localhost
System.print(config["database"]["credentials"]["user"])  // admin

Lists

var data = Yaml.parse("
languages:
  - Wren
  - C
  - Python
")
for (lang in data["languages"]) {
  System.print(lang)
}

Lists of Maps

var nav = Yaml.parse("
pages:
  - file: index
    title: Home
  - file: about
    title: About Us
")
for (page in nav["pages"]) {
  System.print(page["title"])
}

Comments

var data = Yaml.parse("
# This is a comment
name: test
# Another comment
value: 123
")
System.print(data["name"])  // test

Data Types

var types = Yaml.parse("
string: hello world
number: 42
float: 3.14
bool_true: true
bool_false: false
null_value: null
tilde_null: ~
quoted: \"with:special chars\"
")
System.print(types["string"])     // hello world (String)
System.print(types["number"])     // 42 (Num)
System.print(types["bool_true"])  // true (Bool)
System.print(types["null_value"]) // null

Type Mapping

Examples

Configuration File

import "yaml" for Yaml
import "io" for File

var config = Yaml.parse(File.read("config.yaml"))
System.print("Server: %(config["server"]["host"]):%(config["server"]["port"])")
System.print("Database: %(config["database"]["url"])")

Building and Stringifying

import "yaml" for Yaml

var data = {
    "name": "Project",
    "version": "1.0.0",
    "dependencies": ["wren", "libuv"],
    "settings": {
        "debug": true,
        "timeout": 30
    }
}

System.print(Yaml.stringify(data))

Round-Trip

import "yaml" for Yaml

var original = "
title: Test
items:
  - first
  - second
"
var parsed = Yaml.parse(original)
var reserialized = Yaml.stringify(parsed)
var reparsed = Yaml.parse(reserialized)

System.print(parsed["title"] == reparsed["title"])  // true