Lua

Lua is a scripting imperative and scripting language first appearing in 1993.

Hello World

#!/usr/bin/env lua5.4

print("Hello World!")

Coding Guide

Language Version

Lua 5.4

Execution Model

• Interpreted, runs directly from source
• Fragment executes inside a main() function
• Interpreter launches once, runs main(), then exits
• Output must be explicit (print, io.write)

Key Characteristics

• Dynamic typing
• Case-sensitive
• Tables are the primary data structure
• Prefer local variables to avoid leaking globals

Fragment Authoring

Write valid Lua statements. Your fragment becomes the main function body. Code runs inside the main function, then the interpreter exits. Define helper functions before using them.

Available Packages

Standard libraries are available:

• string - string manipulation
• table - table operations
• math - mathematical functions
• io - input/output operations
• os - operating system interface

Common Patterns

• Print: print("message")
• Local variables: local message = "Hello"
• Tables: local list = {1, 2, 3}
• Functions: local function greet(name) return string.format("Hi, %s", name) end
• Iteration: for i, value in ipairs(list) do ... end
• Table iteration: for key, value in pairs(table) do ... end

Examples

-- Simple output
print("Hello, World!")

-- Function definition
local function greet(name)
  return string.format("Hello, %s!", name)
end

print(greet("Alice"))

-- Table processing
local numbers = {1, 2, 3, 4, 5}
local sum = 0
for i, value in ipairs(numbers) do
  sum = sum + value * value
end
print(string.format("Sum of squares: %d", sum))

Caveats

• Globals persist only for the single run
• Use local to avoid polluting the global namespace
• External require calls only work if the module exists in the runtime environment

Fraglet Scripts

Echo Args

#!/usr/bin/env -S fragletc --vein=lua
print("Args: " .. table.concat(arg, " "))

Stdin Upper

#!/usr/bin/env -S fragletc --vein=lua
for line in io.lines() do
    print(string.upper(line))
end

Table Process

#!/usr/bin/env -S fragletc --vein=lua
local numbers = {1, 2, 3, 4, 5}
local sum = 0
for i, value in ipairs(numbers) do
  sum = sum + value * value
end
print(string.format("Sum of squares: %d", sum))

Test

#!/usr/bin/env -S fragletc --vein=lua

print("Hello World!")

Connections

Container Info