Method Calls in AutoLang

This tutorial explains how method calls work in AutoLang, including both regular methods and VM methods.

Overview

AutoLang supports two types of methods:

1. Regular Methods: Defined in ext blocks or type definitions using AutoLang syntax
2. VM Methods: Implemented in Rust (marked with fn.vm) for performance or system-level operations

Both types can be called using the same dot syntax: obj.method(args)

Regular Methods

Regular methods are defined in AutoLang using the ext statement:

ext Point {
    fn distance(self, other Point) int {
        let dx = .x - other.x
        let dy = .y - other.y
        sqrt(dx*dx + dy*dy)
    }
}

// Usage:
fn main() {
    let p1 = Point {x: 0, y: 0}
    let p2 = Point {x: 3, y: 4}
    let d = p1.distance(p2)  // Returns 5
}

Key Features:

• Defined in AutoLang syntax
• Can access instance via self or .property shorthand
• Full control over implementation logic
• Type-checked at compile time

VM Methods

VM methods are implemented in Rust and marked with fn.vm:

ext str {
    /// Split string by delimiter into array of strings
    fn.vm split(delimiter str) []str
    fn.vm lines() []str
    fn.vm words() []str

    /// Get the length of the string
    fn len() int {
        .size  // AutoLang implementation
    }
}

Key Features:

• Implemented in Rust for performance
• Can do system-level operations (file I/O, string processing, etc.)
• Called using same dot syntax as regular methods
• Naming convention: registered as {type}_{method} (e.g., str_split)

Calling Methods

All methods are called using dot syntax:

// Basic method call
let len = "hello".len()  // Returns 5

// Method with arguments
let words = "hello world".split(" ")  // Returns ["hello", "world"]

// Method chaining
let first = "hello world".split(" ")[0]  // Returns "hello"

// Mixed VM and regular methods
let trimmed = "  hello  ".trim().len()  // Returns 5

Method Call Resolution

When you call obj.method(args), the evaluator:

1. Checks for VM methods (for Value::Instance types)

   • Looks in VM_REGISTRY for instances of user-defined types

2. Checks for ext methods (Plan 035)

   • Looks for "TypeName::method_name" in the symbol table
   • Supports both static and instance methods

3. Checks for VM builtin functions (Plan 038)

   • Constructs VM function name: {type}_{method}
   • Looks for str_split, str_lines, etc.
   • Calls VM function with self as first argument

4. Returns error if not found

   • "Invalid dot expression {type}.{method}"

Examples

String Methods

fn main() {
    // VM methods (Plan 038)
    let text = "hello world"
    let words = text.split(" ")      // ["hello", "world"]
    let first = words[0]              // "hello"
    let count = words.len()          // 2

    // AutoLang methods
    let trimmed = text.trim()         // "hello world"
    let upper = text.upper()          // "HELLO WORLD"
    let lower = text.lower()          // "hello world"

    // Method chaining
    let result = text.upper().split(" ")[0]  // "HELLO"
}

File Methods

依赖模块示例

此示例依赖多文件模块，不能在书页内运行——请到 Playground

fn main() {
    use auto.io: File

    // VM methods
    let f = File.open("test.txt")
    let content = f.read_all()       // Read entire file
    f.close()

    // Method chaining
    let lines = File.open("test.txt").read_all().lines()
}

Array Methods

fn main() {
    let arr = [1, 2, 3, 4, 5]

    // Regular methods
    let len = arr.len()              // 5
    let first = arr[0]               // 1
    let last = arr[arr.len() - 1]   // 5
}

When to Use Each Type

Use Regular Methods When:

• ✅ Logic can be expressed in AutoLang
• ✅ You need type-level operations
• ✅ You want full control over implementation
• ✅ Method is simple and doesn't require system access

Examples:

• Data structure methods (Point.distance(), Circle.area())
• Business logic methods
• Algorithm implementations

Use VM Methods When:

• ✅ Performance is critical (string processing, file I/O)
• ✅ Need system-level operations (file access, system calls)
• ✅ Implementation is complex or error-prone in AutoLang
• ✅ Need to interface with C/Rust libraries

Examples:

• String operations (split, trim, replace)
• File I/O (read_all, write_lines)
• Math operations (sqrt, sin, cos)
• System operations (getpid, time)

Best Practices

1. Prefer AutoLang methods for clarity and maintainability
2. Use VM methods for performance-critical code
3. Document VM methods with clear examples
4. Keep method signatures simple and intuitive
5. Use method chaining judiciously (avoid deeply nested chains)

Migration Guide

From Global Functions to Methods

Before (Plan 025 style):

let words = str_split("hello world", " ")
let lines = str_lines("line1\nline2")
let trimmed = str_trim("  hello  ")

After (Plan 038 style):

let words = "hello world".split(" ")
let lines = "line1\nline2".lines()
let trimmed = "  hello  ".trim()

Both syntaxes still work, but the method call syntax is more consistent and idiomatic.

Related Documentation

• Plan 035: ext Statement - Method definition system
• Plan 038: VM Method Call Expressions - Implementation details
• String Methods Reference - Complete string API documentation
• File Methods Reference - File I/O methods

See Also

• Functions - Function definitions and calls
• Types - Type system overview
• ext Statement - Adding methods to types