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L4 Language Reference

The L4 language reference provides precise technical documentation for all language features. Use this section to look up specific keywords, types, operators, and syntax rules.

Contents

📚 GLOSSARY

Master index linking to all language features - start here to find what you need.

Language Components

Functions

Keywords for defining functions and computations:

  • Parameters: GIVEN, GIVETH
  • Definitions: DECIDE, MEANS, YIELD
  • Local bindings: LET, WHERE
  • Aliases: AKA

Types

L4's type system for representing data:

  • Primitives: BOOLEAN, NUMBER, STRING, DATE
  • Type Constructors: DECLARE, IS, HAS, ONE OF
  • Polymorphic Types: LIST, MAYBE, EITHER

Operators

Operations for computing and comparing values:

  • Arithmetic: PLUS, MINUS, TIMES, DIVIDED BY, MODULO
  • Comparison: EQUALS, GREATER THAN, LESS THAN, AT MOST, AT LEAST
  • Logical: AND, OR, NOT, IMPLIES
  • String: CONCAT, APPEND
  • Temporal: AT, WITHIN

Syntax

Structural rules and special syntax patterns:

  • Layout Rules: Indentation-based grouping
  • Comments: -- and {- -}
  • Identifiers: Backtick-quoted names
  • Annotations: @desc, @nlg, @ref, @export
  • Directives: #EVAL, #TRACE, #CHECK, #ASSERT
  • Special Syntax: Ditto (^), Asyndetic (..., ..)

Libraries

Core libraries shipped with L4:

  • prelude: Standard functions (auto-imported)
  • daydate: Date calculations and temporal logic
  • excel-date: Excel date compatibility
  • math: Mathematical functions
  • currency: Currency handling
  • legal-persons: Legal entity types
  • jurisdiction: Jurisdiction definitions