Built-in Functions (Not a Library)

L4 includes several built-in functions that are always available without importing any library. These are implemented in the compiler core.

For operators (arithmetic, comparison, boolean), see also Operators for precedence and usage details.

Type Coercion Builtins

Function	Signature	Description
TOSTRING	NUMBER/BOOLEAN/DATE/TIME/DATETIME → STRING	Convert to string representation
TONUMBER	STRING → MAYBE NUMBER	Parse string to number
TODATE	STRING → MAYBE DATE	Parse string to date
TOTIME	STRING → MAYBE TIME	Parse string to time
TODATETIME	STRING → MAYBE DATETIME	Parse string to datetime
TRUNC	NUMBER, NUMBER → NUMBER	Truncate decimal places
AS STRING	value AS STRING	Inline string conversion

Numeric Builtins

Function	Signature	Description
FLOOR	NUMBER → NUMBER	Round down to integer
CEILING	NUMBER → NUMBER	Round up to integer
ROUND	NUMBER → NUMBER	Round to nearest integer
EXPONENT	NUMBER → NUMBER → NUMBER	Exponentiation (base, power)
LN	NUMBER → MAYBE NUMBER	Natural logarithm
LOG10	NUMBER → MAYBE NUMBER	Base-10 logarithm
SQRT	NUMBER → MAYBE NUMBER	Square root
SIN, COS, TAN	NUMBER → MAYBE NUMBER	Trigonometric functions (radians)
ASIN, ACOS, ATAN	NUMBER → MAYBE NUMBER	Inverse trigonometric functions

String Builtins

Function	Signature	Description
STRINGLENGTH	STRING → NUMBER	Length of string
SUBSTRING	STRING → NUMBER → NUMBER → STRING	Extract substring
TOUPPER	STRING → STRING	Convert to uppercase
TOLOWER	STRING → STRING	Convert to lowercase

Date Builtins

Function	Signature	Description
DATE_FROM_DMY	NUMBER → NUMBER → NUMBER → DATE	Construct DATE from day, month, year
DATE_FROM_SERIAL	NUMBER → DATE	Construct DATE from serial number
DATE_SERIAL	DATE → NUMBER	Get serial number from DATE
DATE_DAY	DATE → NUMBER	Extract day from DATE
DATE_MONTH	DATE → NUMBER	Extract month from DATE
DATE_YEAR	DATE → NUMBER	Extract year from DATE
TODAY	DATE	Current date (requires TIMEZONE IS)

Time Builtins

Function	Signature	Description
TIME_SERIAL	TIME → NUMBER	Get serial number (day fraction) from TIME
CURRENTTIME	TIME	Current local time (requires TIMEZONE IS)

DateTime Builtins

Function	Signature	Description
DATETIME_SERIAL	DATETIME → NUMBER	Get UTC serial number from DATETIME
NOW	DATETIME	Current date and time (defaults to UTC without TIMEZONE IS)

Timezone Builtins

Function	Signature	Description
TIMEZONE	STRING	Returns the document timezone string (requires TIMEZONE IS)
TIMEZONE IS	declaration	Top-level declaration setting the document timezone

Arithmetic Operators

These operators are always available without import.

Operator	Text Alias	Signature	Description
+	PLUS	NUMBER → NUMBER → NUMBER	Addition
-	MINUS	NUMBER → NUMBER → NUMBER	Subtraction
*	TIMES	NUMBER → NUMBER → NUMBER	Multiplication
/	DIVIDED BY	NUMBER → NUMBER → NUMBER	Division
MODULO	--	NUMBER → NUMBER → NUMBER	Remainder
EXPONENT	--	NUMBER → NUMBER → NUMBER	Exponentiation
FLOOR	--	NUMBER → NUMBER	Round down to integer
CEILING	--	NUMBER → NUMBER	Round up to integer
TRUNC	--	NUMBER → NUMBER	Truncate toward zero

Comparison Operators

Operator	Text Alias	Signature	Description
=	EQUALS	a → a → BOOLEAN	Equality (not assignment)
>	GREATER THAN	a → a → BOOLEAN	Greater than
<	LESS THAN	a → a → BOOLEAN	Less than
>=	AT LEAST	a → a → BOOLEAN	Greater than or equal
<=	AT MOST	a → a → BOOLEAN	Less than or equal

Note: = is equality, NOT assignment. L4 has no assignment (pure functional).

Boolean Operators

Operator	Symbol Alias	Precedence	Description
NOT	--	Highest	Logical negation
AND	&&	High	Logical and
OR	||	Medium	Logical or
IMPLIES	=>	Lowest	Logical implication
UNLESS	--	= AND NOT	Shorthand for AND NOT

String Operations

Function	Signature	Description
CONCAT x, y, ...	STRING → ... → STRING	Concatenate multiple strings
CONTAINS	STRING → STRING → BOOLEAN	Substring test
STARTS WITH	STRING → STRING → BOOLEAN	Prefix test
ENDS WITH	STRING → STRING → BOOLEAN	Suffix test
INDEXOF	STRING → STRING → NUMBER	Find position of substring
SPLIT	STRING → STRING → LIST OF STRING	Split by delimiter
CHARAT	STRING → NUMBER → STRING	Character at index
SUBSTRING	STRING → NUMBER → NUMBER → STRING	Substring (str, start, length)
STRINGLENGTH	STRING → NUMBER	String length
TOUPPER	STRING → STRING	Convert to uppercase
TOLOWER	STRING → STRING	Convert to lowercase

List Construction

Syntax	Description
LIST x, y, z	Literal list
EMPTY	Empty list
x FOLLOWED BY xs	Cons (prepend)

Nullary Builtins

Function	Type	Description
TODAY	DATE	Current date in document timezone
TIMEZONE	STRING	Document timezone (IANA name)

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HTTP and JSON Builtins

Function	Signature	Description
FETCH	STRING → STRING	HTTP GET request
POST	STRING, STRING, STRING → STRING	HTTP POST request
ENV	STRING → STRING	Read environment variable
JSONENCODE	a → STRING	Convert value to JSON string
JSONDECODE	STRING → EITHER STRING a	Parse JSON string to value

For detailed HTTP/JSON documentation, see HTTP and JSON.

For detailed coercion documentation, see Coercions.