Lexicon

Go, Interpreters

Lexicon - Sprout Programming Language Interpreter 🌱

Lexicon is an interpreter for Sprout, a small programming language written in Go. It implements a full pipeline — lexer, parser, AST, and evaluator — and includes an interactive REPL for exploring expressions, variables, and control flow. The project is designed to teach core concepts of language design and interpreter implementation.

Quick Start

Build the Interpreter

./run.sh

Run REPL

./sprout

Run Sprout Files

./sprun filename.spr

Run with Trace Mode

./sprun --trace filename.spr

Run with Debug Logging

./sprun --debug filename.spr

Interactive Session

sprout> sprout x = 10;
sprout> sprout y = 20;
sprout> echo x + y;
30
sprout> trace on
Trace mode enabled!
sprout> help

Features

  • Lexer - Tokenizes Sprout source code with line/column tracking
  • Parser - Builds Abstract Syntax Tree (AST) with error collection
  • Interpreter - Executes Sprout programs with full error handling
  • REPL - Interactive command-line interface with environment inspection
  • Error Reporting - Detailed errors with line and column numbers
  • Trace Execution - Step-by-step debugging mode
  • Logging System - Internal state logging for debugging
  • Documentation - Comprehensive guides for usage

Language Overview

Variables & Types

sprout x = 10              # Integer
sprout pi = 3.14           # Float
sprout name = "Sprout"     # String
sprout flag = true         # Boolean

# With type annotations
sprout age int = 25
sprout price float = 19.99

Operators

  • Arithmetic: + - * / % **
  • Comparison: < > <= >= == !=
  • Logical: && || ! (or and or not)

Control Flow

if (x > 5) {
    echo "Greater";
} else {
    echo "Smaller";
}

Comments

# This is a comment
sprout x = 10;  # Inline comment

REPL Commands

  • help - Show help and language features
  • env - Show all variables
  • clear - Clear environment
  • trace on - Enable trace execution
  • trace off - Disable trace execution
  • exit - Quit REPL

Error Reporting

Sprout provides detailed error messages with line and column information:

[Line 5:10] Expected next token to be =, got ; instead
ERROR [Line 3:5]: identifier not found: myVariable
ERROR: division by zero
ERROR: type mismatch: INTEGER + STRING

Debugging Features

Trace Execution

See step-by-step execution of your code:

./sprun --trace examples/examples.spr

Output:

[TRACE] Eval: *ast.Program
[TRACE]   Eval: *ast.VariableDeclaration
[TRACE]     VariableDeclaration: x
[TRACE]       IntegerLiteral: 10
[TRACE]     Set variable x = 10

Environment Inspection

In REPL, use env to see all variables:

sprout> env
Current environment variables:
  x = 10
  y = 20

Documentation

Comprehensive documentation is available in the /docs directory:

Project Structure

Lexicon/
├── cmd/
│   ├── repl/          # Interactive REPL
│   └── demo/          # File executor
├── src/
│   ├── token/         # Token definitions
│   ├── lexer/         # Lexical analyzer
│   ├── parser/        # Parser and AST
│   ├── ast/           # AST node definitions
│   ├── evaluator/     # Interpreter
│   └── logger/        # Logging system
├── docs/              # Documentation
├── examples/          # Example programs

Testing

go test ./src/lexer      # Lexer tests
go test ./src/parser     # Parser tests
go test ./src/evaluator  # Evaluator tests
go test ./...            # All tests

Authors