MAIN-FUNCTION

Main Function in VintLang

VintLang now supports a main function as an entry point for your programs, similar to Go, Zig, C, and C++. This provides a structured way to organize your code while maintaining full backward compatibility.

How It Works

Two-Phase Execution Model

1. Setup Phase: All top-level statements are executed to define functions, variables, and perform initialization
2. Main Phase: If a main function is found, it's automatically called as the program's entry point

Main Function Syntax

Use VintLang's existing function syntax to define a main function:

let main = func() {
    println("Hello from main!")
    return 0
}

Or with const:

const main = func() {
    println("Hello from main!")
    return "success"
}

Complete Example

// Setup phase - runs first
import time
println("🚀 Program starting...")

// Define helper functions
let greet = func(name) {
    println("Hello,", name, "!")
}

let calculate = func(a, b) {
    return a + b
}

// Main function - entry point
let main = func() {
    println("=== Main Function ===")
    
    greet("Developer")
    let result = calculate(10, 20)
    println("Result:", result)
    println("Time:", time.now())
    
    return result
}

// More setup
println("⚙️ Setup complete")

Output:

🚀 Program starting...
⚙️ Setup complete
=== Main Function ===
Hello, Developer !
Result: 30
Time: 16:42:00 26-09-2025
30

Main Function Features

Parameters

Main functions currently don't receive command-line arguments, but this could be extended in the future:

let main = func() {
    // No parameters for now
    println("Main executed")
}

Return Values

The main function's return value becomes the program's final result:

let main = func() {
    return 42  // This will be printed as the program output
}

Error Handling

If the main function returns an error, it will be propagated:

let main = func() {
    if (someCondition) {
        return error("Something went wrong")
    }
    return "success"
}

Backward Compatibility

Programs without a main function continue to work exactly as before:

// This still works - no main function needed
println("Hello World")
let x = 42
println("x =", x)

When to Use Main Functions

Use main functions when:

• Building larger, structured programs
• You want clear separation between setup and execution
• Coming from Go, C, C++, or similar languages
• Building command-line tools or applications

Stick with the traditional approach when:

• Writing simple scripts
• Prototyping or testing small code snippets
• Using VintLang in REPL mode
• Personal preference for simpler structure

Execution Flow

1. Parse the entire program
2. Setup Phase: Execute all top-level statements
   • Define variables with let and const
   • Define functions
   • Run imports
   • Execute setup code
3. Main Phase: If main function exists, call it
4. Return either the main function's result or the last statement's result

Migration Guide

To convert existing VintLang programs to use main functions:

Before:

import time
let x = 42
println("Hello World")
println("Time:", time.now())

After:

import time  // Still runs in setup phase

let main = func() {
    let x = 42
    println("Hello World")  
    println("Time:", time.now())
}

The behavior remains identical, but the code is now more structured and explicit about the entry point.