interpreter.md

Interpreter

Table of Contents

• Overview
• Main Interpreter Functions
• Flow Control with InterpretResult
• Summary of Steps
• Example Execution Flow
• Error Handling

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Overview

The interpreter takes the AST and executes it. In FlavorLang, this means:

1. Evaluating Expressions
2. Assigning / Retrieving Variables
3. Managing Conditionals & Loops
4. Handling Function Calls
5. Printing & Error Handling

Main Interpreter Functions

• interpret_node(...): The primary function that returns an InterpretResult, containing a LiteralValue plus a did_return flag indicating if a function return (deliver) occurred.
• interpret_assignment(...): Assigns values to variables in the environment.
• interpret_binary_op(...): Applies arithmetic or comparison operators to numeric or string values.
• interpret_conditional(...): Runs if/elif/else logic, short-circuiting if a deliver statement is hit.
• interpret_while_loop(...): Evaluates a loop’s condition repeatedly, stopping if did_return is set or condition is false.
• interpret_function_call(...): Creates a local environment for function parameters, executes the function body, and handles the final return value.

Flow Control with InterpretResult

• interpret_node(...) always returns an InterpretResult:
• .value = The LiteralValue result of the node.
• .did_return = true if a deliver statement was encountered, letting parent code know to halt further statements.
• This approach ensures something like the following stops interpreting once deliver 1; is returned in the base case:

create factorial(n) {
   if n <= 1 {
      deliver 1;
   } else {
      deliver n * factorial(n - 1);
   }
}

let result = factorial(3);

Example Execution Flow

For x = 5 + 3:

1. interpret_node(AST_ASSIGNMENT) → calls interpret_assignment().
2. interpret_node(RHS: AST_BINARY_OP) → calls interpret_binary_op().
3. interpret_node(left=5) returns 5; similarly right=3 returns 3.
4. After 5 + 3 = 8, store x = 8 in the environment.

Error Handling

• Checks for undefined variables, invalid operator usage, division by zero, etc.
• On error, prints a message and calls exit(1).

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License

This project is licensed under the Apache 2.0 License — see the LICENSE file for details.

© 2024-2025 Kenneth Oliver. All rights reserved.