ITMOScript Interpreter

A dynamically-typed interpreted programming language implemented in C++.

Overview

ITMOScript interpreter executes .is source files with features including first-class functions, lists, strings, and standard control flow constructs. The implementation follows a classic multi-pass architecture: Lexer -> Parser -> AST -> Tree-walking Evaluator.

Architecture

• Lexer - Tokenizes source code (numbers, strings, identifiers, operators, keywords)
• Parser - Recursive descent parser produces an AST with operator precedence
• Interpreter - Tree-walking evaluator with dynamic typing and garbage collection via shared_ptr
• Scope - Lexical scoping with parent chains for variable lookup and assignment

Language Features

• Dynamic typing - Types checked at runtime, Python-like copy/value semantics
• Data types - Numbers (double), strings, lists, booleans, nil, first-class functions
• Operators - Arithmetic, comparison, logical (and/or/not), indexing/slicing
• Control flow - if/else if/else, while, for-in loops, break/continue
• Functions - First-class, higher-order, lexical closures, return statements
• Comments - Single-line // comments

Standard Library

Math: abs, ceil, floor, round, sqrt, rnd, parse_num, to_string
Strings: len, lower, upper, split, join, replace
Lists: range, len, push, pop, insert, remove, sort
System: print, println, read, stacktrace

Building

cmake -B build
cmake --build build

Usage

#include "interpreter.h"

std::istringstream input("println(\"Hello, ITMOScript!\")");
std::ostringstream output;
interpret(input, output);

Requirements

• C++17 or later
• CMake 3.10+
• Google Test (for unit tests)

Project Structure

File	Description
lexer.h/lexer.cpp	Tokenizer with keyword map
token.h/token.cpp/token_type.h	Token types and values
ast.h	AST node definitions (20+ node types)
parser.h/parser.cpp	Recursive descent parser with precedence climbing
interpreter.h/interpreter.cpp	Main evaluation loop and entry point
value.h	Variant-based dynamic value type
scope.h/scope.cpp	Lexical scope with parent chain
function.h	User-defined function representation
standart_library_func.h/standart_library_func.cpp	Built-in functions

Error Handling

All runtime errors (type mismatches, out-of-bounds access, undefined variables) throw exceptions caught by the interpreter, with stack trace support via stacktrace().