Quick Start

Get started with Levython in minutes. This guide will walk you through writing and running your first programs.

Hello World#

Create a file named hello.levy:

say("Hello, World!")

Run it:

$ levython hello.levy
Hello, World!

File Extensions#

Levython supports two file extensions:

• .levy - Full extension (recommended)
• .ly - Short extension

Both are fully supported and equivalent:

levython hello.levy   # Works
levython hello.ly     # Also works

A Basic Program#

Here's a comprehensive example demonstrating core Levython features including functions, variables, control flow, and iteration:

# A simple calculator demonstrating Levython features

# Function definitions use 'act' keyword
# Returns use '->' operator
act add(a, b) {
    -> a + b
}

act subtract(a, b) {
    -> a - b
}

act multiply(a, b) {
    -> a * b
}

act divide(a, b) {
    if b == 0 {
        say("Error: Division by zero")
        -> 0
    }
    -> a / b
}

# Variable assignment uses '<-' operator
x <- 10
y <- 5

# Output with say() function
say("Calculator Demo")
say("===============")
say(str(x) + " + " + str(y) + " = " + str(add(x, y)))
say(str(x) + " - " + str(y) + " = " + str(subtract(x, y)))
say(str(x) + " * " + str(y) + " = " + str(multiply(x, y)))
say(str(x) + " / " + str(y) + " = " + str(divide(x, y)))

# Conditional execution
if x > y {
    say(str(x) + " is greater than " + str(y))
} else {
    say(str(y) + " is greater than " + str(x))
}

# Iteration with for loops
say("")
say("Counting to 5:")
for i in range(1, 6) {
    say("  " + str(i))
}

# Working with lists
say("")
say("Computing squares:")
numbers <- [1, 2, 3, 4, 5]
for n in numbers {
    square <- multiply(n, n)
    say("  " + str(n) + " squared = " + str(square))
}

Output:

Calculator Demo
===============
10 + 5 = 15
10 - 5 = 5
10 * 5 = 50
10 / 5 = 2
10 is greater than 5

Counting to 5:
  1
  2
  3
  4
  5

Computing squares:
  1 squared = 1
  2 squared = 4
  3 squared = 9
  4 squared = 16
  5 squared = 25

Interactive Input

Levython supports interactive user input with the ask() function:

# Get user input
name <- ask("What is your name? ")
say("Hello, " + name + "!")

# Input can be converted to numbers
age_str <- ask("What is your age? ")
age <- int(age_str)

if age >= 18 {
    say("You are an adult.")
} else {
    say("You are a minor.")
}

Syntax Highlights

Running Examples#

Levython comes with 10 tutorial examples in the examples/ directory:

Run any example:

levython examples/01_hello_world.levy

Next Steps#

Now that you've run your first Levython programs, dive deeper into the language features:

Core Language

• Variables & Data Types - Numbers, strings, booleans, lists, and type conversion
• Functions - Defining functions with act, parameters, returns, and recursion
• Control Flow - Conditional execution with if/elif/else
• Loops - Iteration with for and while loops
• Lists & Collections - Creating, accessing, and manipulating lists

Input/Output & Files

• Input/Output - User input with ask() and output formatting
• File System - Reading and writing files, directory operations

Advanced Topics

• Performance Optimization - Understanding JIT compilation and optimization techniques
• Memory Management - Direct memory operations and NaN-boxing internals
• Bitwise Operations - Low-level bit manipulation
• Tensor Operations - High-performance multi-dimensional arrays for ML/AI
• SIMD Vectorization - Parallel data processing with vector instructions

Tools & Ecosystem

• Command Line Interface - All CLI options and flags
• Package Manager (LPM) - Installing and managing packages
• VS Code Extension - Syntax highlighting, snippets, and debugging

REPL Mode

Levython includes an interactive REPL (Read-Eval-Print Loop) for experimenting with code:

$ levython
Levython 1.0.0 REPL
Type 'exit' to quit

>>> x <- 42
>>> say(str(x * 2))
84
>>> act square(n) { -> n * n }
>>> square(7)
49
>>> exit

The REPL is perfect for quick calculations, testing functions, and learning the language interactively.