Phase 3: Function Execution Engine

Objective

Implement function call resolution, execution, and return value handling.

Function Call Syntax

// Simple calls
greet("World")
add(5, 3)

// Nested calls
print(greet("XMD"))
cmd("echo " + add(2, 3))

// Variable usage
set result = add(x, y)
print(result)

Components to Build

1. Function Call Parser

  • File: src/function/parse_function_call/parse_function_call.c
  • Purpose: Parse function call syntax and extract arguments
  • Handle: func(), func(arg), func(a, b, c)

2. Argument Evaluator

  • File: src/function/evaluate_arguments/evaluate_arguments.c
  • Purpose: Evaluate arguments before passing to function
  • Handle: Variables, strings, numbers, nested calls

3. Function Executor

  • File: src/function/execute_function/execute_function.c
  • Purpose: Execute user-defined function with arguments
  • Process: Create scope, bind parameters, execute body, return result

4. Scope Manager

  • File: src/function/scope_manager/scope_manager.c
  • Purpose: Manage local variable scope during function execution
  • Operations: create_scope, bind_parameter, resolve_variable, destroy_scope

5. Return Value Handler

  • File: src/function/return_handler/return_handler.c
  • Purpose: Handle function return statements and values
  • Support: return value;, return "string";, return variable;

Function Call Processor

  • File: src/xmd_processor/process_function_call/process_function_call.c
  • Purpose: Main entry point for function call processing
  • Integration: Modify process_directive.c to recognize function calls

Execution Flow

  1. Parse function call → extract name and arguments
  2. Lookup function in registry → get function definition
  3. Evaluate arguments → resolve variables and expressions
  4. Create local scope → bind parameters to arguments
  5. Execute function body → process XMD directives in function context
  6. Handle return → extract return value and cleanup scope
  7. Return result → substitute function call with result

Advanced Features

  • Recursion: Support for recursive function calls
  • Nested Calls: Functions calling other functions
  • Error Handling: Meaningful errors for missing functions/parameters
  • Type Coercion: Automatic string/number conversion

Success Criteria

  • Function calls resolve correctly
  • Parameters passed accurately
  • Return values work properly
  • Local scope isolated from global
  • Recursive calls supported
  • Performance acceptable for reasonable nesting

Error Handling

  • Function not found
  • Wrong number of arguments
  • Invalid argument types
  • Stack overflow (deep recursion)
  • Runtime errors in function body

Dependencies

  • Phase 1: Multiline output fixed
  • Phase 2: Function definitions working
  • Existing variable system
  • Existing directive processing