VirtLang is a custom-built programming language interpreter written in Go, designed for extensibility, clarity, and hackability. It powers a full-language runtime with native support for variables, functions, control flow, error handling, and complex types.

VirtLang features a clean three-stage architecture:

1. Lexing (lexer.Tokenize()) — converts source code into tokens
2. Parsing (parser.ProduceAST()) — builds an Abstract Syntax Tree (AST)
3. Evaluation (evaluator.Evaluate()) — runs the AST and produces results

The AST separates logic into:

• Stmt → non-returning statements (like let, while, if)
• Expr → return-producing expressions (like 1 + 2, "hello")

Runtime is powered by:

• A unified RuntimeValue type system
• Scoped environments for variable resolution
• Support for both native and user-defined functions

• let and const declarations
• Functions (closures, parameters, call support)
• Control flow: if, else, while
• Structured error handling: try, catch
• Rich type system: numbers, strings, booleans, arrays, objects
• Member access (obj.key) and array indexing (arr[i])
• Binary, logical, and comparison operators

Here's a minimal example showing how to evaluate VirtLang code in Go:

package main

import (
    "fmt"

    "github.com/dev-kas/virtlang-go/v4/environment"
    "github.com/dev-kas/virtlang-go/v4/evaluator"
    "github.com/dev-kas/virtlang-go/v4/parser"
)

func main() {
    code := `let n = 1
while (n < 10) {
    n = n + 1
}
n // output: 10`

    // Set up parser and global environment
    p := parser.New("demo")
    env := environment.NewEnvironment(nil)

    // Parse source code into AST
    program, err := p.ProduceAST(code)
    if err != nil {
        fmt.Printf("Syntax error: %v\n", err)
        return
    }

    // Evaluate AST
    result, runErr := evaluator.Evaluate(program, env, nil)
    if runErr != nil {
        fmt.Printf("Runtime error: %v\n", runErr)
        return
    }

    // Display result
    fmt.Printf("Result: %v (Type: %v)\n", result.Value, result.Type)
}

• Auto-generated Go package docs: DOCS.md
• Full design write-up and architecture: VirtLang Wiki

Found a bug? Want to add a feature? See CONTRIBUTING.md for guidelines.