#MoonBit Eval

#Introduction

#Progress

• Expression
• Variable
• Basic Types
• If
• Let (Mut)
• Assign
• For
• While
• Lambda Fn
• Struct
• Match
• Trait

#Examples

#Basic Operations

test "basic" {
  let vm = MoonBitVM::new()
  inspect(vm.eval("1 + 1"), content="2")
  inspect(vm.eval("5 * 3"), content="15")
  inspect(vm.eval("10 / 2"), content="5")
  inspect(vm.eval("5 == 5"), content="true")
  inspect(vm.eval("\"hello\" + \"world\""), content="helloworld")
}

#Variables and Functions

test "variables and functions" {
  let vm = MoonBitVM::new()
  inspect(vm.eval("let a = 1"), content="()")
  inspect(vm.eval("a"), content="1")

  inspect(vm.eval("fn add(a: Int, b: Int) -> Int { a + b }"), content="(a: Int, b: Int) -> Int")
  inspect(vm.eval("add(1, 2)"), content="3")
}

#Mutable Variables

test "mutable variables" {
  let vm = MoonBitVM::new()
  inspect(vm.eval("let mut a = 1"), content="()")
  inspect(vm.eval("a = 12"), content="()")
  inspect(vm.eval("a"), content="12")
}

#Control Flow

test "control flow" {
  let vm = MoonBitVM::new()
  inspect(vm.eval("if 1 > 0 { 3 } else { 4 }"), content="3")

  inspect(vm.eval("let mut sum = 0"), content="()")
  inspect(vm.eval("for i = 0; i < 5; i = i + 1 { sum += i }"), content="()")
  inspect(vm.eval("sum"), content="10")
}

#Lambda Functions

test "lambda" {
  let vm = MoonBitVM::new()
  inspect(vm.eval("let f = x => x * 2"), content="()")
  inspect(vm.eval("f(3)"), content="6")

  inspect(vm.eval("let h = z => z * z"), content="()")
  inspect(vm.eval("h(4)"), content="16")
}

#Structs and Methods

test "struct" {
  let vm = MoonBitVM::new()
  inspect(
    vm.eval(
      #|struct S { 
      #|  a: Int
      #|  b: Int
      #|}
      #|fn S::sum(self: S) -> Int {
      #|  self.a + self.b
      #|}
      top=true,
    ),
    content="()",
  )
  inspect(vm.eval("let s = { a: 23, b: 32 }"), content="()")
  inspect(vm.eval("s.sum()"), content="55")
}

#Fibonacci Recursion

test "fibonacci" {
  let vm = MoonBitVM::new()
  inspect(
    vm.eval(
      #|fn fib(n : Int) -> Int {
      #|  if n <= 1 {
      #|    1
      #|  } else {
      #|    fib(n - 1) + fib(n - 2)
      #|  }
      #|}
    ),
    content="(n: Int) -> Int",
  )
  inspect(vm.eval("fib(10)"), content="89")
}

#External Functions

test "extern" {
  let vm = MoonBitVM::new()
  vm.interpreter.add_extern_fn("println", params => {
    if params is More(Constant(c=String(s), ..), ..) {
      println(s)
    }
    unit()
  })
  inspect(vm.eval("println(\"Hello from external function\")"), content="()")
}

#Match Expressions

test "match" {
  let vm = MoonBitVM::new()
  // 基本常量匹配
  inspect(vm.eval("let s = 10"), content="()")
  inspect(vm.eval("match s { 10 => 100 }"), content="100")

  // 变量模式匹配
  inspect(vm.eval("match 42 { x => x * 2 }"), content="84")

  // 通配符模式匹配
  inspect(vm.eval("match 123 { _ => 999 }"), content="999")

  // Or模式匹配
  inspect(vm.eval("match 5 { 1 | 5 | 10 => 100 }"), content="100")
  inspect(vm.eval("match 3 { 1 | 5 | 10 => 100; _ => 200 }"), content="200")

  // 测试简单变量绑定
  inspect(vm.eval("match 42 { x => x }"), content="42")

  // Tuple模式匹配 - 简化测试
  inspect(vm.eval("match (1, 2) { (a, b) => a }"), content="1")
  inspect(vm.eval("match (1, 2) { (a, b) => b }"), content="2")
  inspect(vm.eval("match (1, 2) { (a, b) => a + b }"), content="3")

  // Array模式匹配
  inspect(vm.eval("match [1, 2, 3] { [a, b, c] => a + b + c }"), content="6")
  inspect(vm.eval("match [5, 10] { [x, y] => x * y }"), content="50")

  // Record模式匹配
  inspect(vm.eval("match { x: 10, y: 20 } { { x, y } => x + y }"), content="30")
  inspect(
    vm.eval("match { name: \"Alice\", age: 25 } { { name, .. } => name }"),
    content="Alice",
  )
  inspect(
    vm.eval("match { name: \"Alice\", age: 25 } { { age, .. } => age }"),
    content="25",
  )
  // 嵌套模式匹配
  inspect(
    vm.eval("match (1, [2, 3]) { (a, [b, c]) => a + b + c }"),
    content="6",
  )

  // 多个case的匹配
  inspect(vm.eval("match 2 { 1 => 10; 2 => 20; _ => 30 }"), content="20")
  inspect(vm.eval("match 5 { 1 => 10; 2 => 20; _ => 30 }"), content="30")
}

#Features

• ✅ Complete Expression Support: Arithmetic, logical, and comparison operations
• ✅ Variable Management: Immutable and mutable variable declarations
• ✅ Control Flow: If-else statements, for loops, while loops
• ✅ Function Definitions: Named functions with parameters and return types
• ✅ Lambda Expressions: Anonymous functions with closure support
• ✅ Struct Definitions: Custom data types with methods
• ✅ Match Expressions: Pattern matching with constant and variable patterns
• ✅ External Functions: Integration with external function calls
• ✅ Type System: Basic type checking and inference

#Contributing

#Community

• QQ Group: 949886784