Functions¶

This folder documents Catalyst function declarations, calls, parameters, comptime fn callability, function types, function pointers, default parameters, error returns, and inference.

Read In This Order¶

• Function Shape and Capabilities: declaration shape, capability parameter convention, concrete context records, and structural capability constraints.
• Destructuring Parameters: struct and array destructuring in parameter binding sites.
• Function Types and Pointers: function type expressions, function item values, C-like function pointers, method pointers, calling conventions, and function type identity.
• Default Parameters: default value rules, suffix omission, and default/capability interaction.
• Error Returns and Inference: T!E, T!, T!Error, main, and signature inference.

Boundary¶

V1 includes:

• named function declarations
• compile-time-only function declarations
• methods as ordinary receiver-first functions
• expression-bodied arrow functions
• destructured parameters
• default parameters
• function item values
• C-like function pointers for concrete signatures

Deferred:

• anonymous function expressions, bound method values, closures, and captures: CEP-0017: Function Literals and Callable Values
• overload sets: CEP-0004: Function Overloading
• named arguments: CEP-0015: Named Arguments
• comptime parameter inference: CEP-0016: Generic Parameter Inference
• comptime-only contract operations: CEP-0034: Comptime-Only Contract Operations
• function-value behavior for defaults: CEP-0017: Function Literals and Callable Values

Related Details¶

• Capabilities and Destructuring
• Errors
• Function Reflection
• Contract Dispatch