kdl is a document language, mostly based on SDLang, with xml-like semantics that looks like you're invoking a bunch of CLI commands!
It's meant to be used both as a serialization format and a configuration language, and is relatively light on syntax compared to XML.
The basic syntax is similar to SDLang:
// This is a node with a single string value
title "Hello, World"
// Multiple values are supported, too
bookmarks 12 15 188 1234
// Nodes can have properties
author "Alex Monad" email="alex@example.com" active=true
// Nodes can be arbitrarily nested
contents {
section "First section" {
paragraph "This is the first paragraph"
paragraph "This is the second paragraph"
}
}
// Nodes can be separated into multiple lines
title \
"Some title"
// Comment formats:
// C++ style
/*
C style multiline
*/
tag /*foo=true*/ bar=false
But kdl changes a few details:
// Files must be utf8 encoded!
smile "😁"
// Instead of anonymous nodes, nodes and properties can be wrapped
// in "" for arbitrary node names.
"!@#$@$%Q#$%~@!40" "1.2.3" "!!!!!"=true
// The following is a legal bare identifier:
foo123~!@#$%^&*.:'|<>/?+ "weeee"
// kdl specifically allows properties and values to be
// interspersed with each other, much like CLI commands.
foo bar=true "baz" quux=false 1 2 3
// strings can be multiline as-is, without a different syntax.
string "my
multiline
value"
// raw/unescaped strings use the "r" prefix on string literals and
// otherwise behave the same, including multiline support.
raw r"C:\Users\kdl"
// You can add any number of # after the r and the last " to
// disambiguate literal " characters.
other-raw r#"hello"world"#
// There is a single decimal number type, much like JSON's.
num 1.234e-42
// Numbers can have underscores to help readability:
bignum 1_000_000
// There is additional support for literal hexadecimal, octal, and binary input.
my-hex 0xdeadbeef
my-octal 0o755
my-binary 0b1010_1101
The following SDLang features are removed altogether:
- "Anonymous" nodes
- Binary data literals
- Date/time formats
onandoffbooleans- Backtick strings
- Semicolons
- Namespaces with
: - Shell style (
#) and Lua-style (--) comments - Distinction between 32/64/128-bit numbers. There's just numbers.
kdl is still extremely new, and discussion about the format should happen over on the discussions page. Feel free to jump in and give us your 2 cents!
nodes := linespace* (node (newline nodes)? linespace*)?
node := identifier (node-space node-argument)* (node-space node-document)? single-line-comment?
node-argument := prop | value
node-children := '{' nodes '}'
node-space := ws* escline ws* | ws+
identifier := [a-zA-Z] [a-zA-Z0-9!$%&'*+\-./:<>?@\^_|~]* | string
prop := identifier '=' value
value := string | raw_string | number | boolean | 'null'
string := '"' character* '"'
character := '\' escape | [^\"]
escape := ["\\/bfnrt] | 'u{' hex-digit{1, 6} '}'
hex-digit := [0-9a-fA-F]
raw-string := 'r' raw-string-hash
raw-string-hash := '#' raw-string-hash '#' | raw-string-quotes
raw-string-quotes := '"' .* '"'
number := decimal | hex | octal | binary
decimal := integer ('.' [0-9]+)? exponent?
exponent := ('e' | 'E') integer
integer := sign? [0-9] [0-9_]*
sign := '+' | '-'
hex := '0x' hex-digit (hex-digit | '_')*
octal := '0o' [0-7] [0-7_]*
binary := '0b' ('0' | '1') ('0' | '1' | '_')*
boolean := 'true' | 'false'
escline := '\\' ws* (single-line-comment | newline)
linespace := newline | ws | single-line-comment
newline := ('\r' '\n') | '\n'
ws := bom | ' ' | '\t' | multi-line-comment
single-line-comment := '//' ('\r' [^\n] | [^\r\n])* newline
multi-line-comment := '/*' ('*' [^\/] | [^*])* '*/'
The above grammar/spec is licensed CC-BY-SA. The included LICENSE.md file in this repository only covers this implementation.