Lumen

Lumen is a simple user-friendly configuration format.

Assignments

Assign values using the key = value format. Values can be reassigned. Semicolons are optional.

key = "value"
key = 42;

Keys

Keys should start with either a letter or an underscore, and then they may also contain digits and hyphens. Lumen is case-sensitive.

_This-Key_IsAllowed1 = true

Keys may be enclosed in ` and are parsed exactly like strings:

`123` = 123
`A Key ` = "A key with spaces"
`\n` = "Newline character"
`!*&([{}++-...\`.` = true

Comments

Comments start with a #.

# A comment

Types

There are 6 data types:

• int
• bool
• float
• string
• array
• object

Numbers

Positive numbers may be optionally prefixed with a plus sign. Negative numbers are prefixed with a minus sign.

int = +42
int = 42
int = -42

float = +0.42
float = 0.42
float = -0.42

Underscores between digits are allowed.

long-number = 123456789
long-number = 123_456_789

long-number = 12345.6789
long-number = 12_345.6_789

Unsigned integers may also be expressed in HEX, OCT or BIN.

hex = 0xFF
hex = 0xF_F

oct = 0o77
oct = 0o7_7

bin = 0b11
bin = 0b1_1

Scientific notation is supported.

float = 314e-2
float = 0.314e+1
float = 0.314e1

Booleans

Booleans can be either true or false.

boolean = true
boolean = false

Strings

Strings are enclosed in either " or '. Escape sequences are allowed.

string = "This is a \t 'string'. \n"

Strings can last multiple lines.

message = "
A
Long
Message
"

Arrays

Arrays are defined using []. Values of different types can be used. Commas are optional. Trailing commas are allowed.

fruits = [ "apple", "orange" ]
fruits = [
    "apple"
    "orange",
]

Objects

Objects are defined using {}. Commas are optional. Trailing commas are allowed.

user = { name = "John", active = true }
user = {
    name = "John",
    active = true,
}

Key Paths

A key path is a sequence of keys split with a ..

# This
settings.search-engine = "google"

# Is an equivalent of this
settings = {
    search-engine = "google"
}

websites.`www.google.com` = true

Key paths are scoped when assigning values inside of an object.

# This
user = {
    address.city = "City"
    address.street = "Street"
}

# Is the same as this
user = {
    address = { city = "City", street = "Street" }
}

Referencing Previous Values

You can reference previously defined values using key paths.

colors.red = "#ff0000"
colors.green = "#00ff00"
colors.blue = "#0000ff"

background-color = colors.red
foreground-color = colors.green

When referencing values, key paths are globally scoped.

colors.red = "#ff0000"
colors.green = "#00ff00"
colors.blue = "#0000ff"

colorscheme = {
    background = colors.red
    foreground = colors.green
}

Implementations

Language	Repository
C++	https://github.com/veevol/lumencpp

File Extensions

Lumen files should use the .lm file extension.