Add comprehensive language features for calculator example

- Add type definition support (type, struct) to AST and parser
- Add binary expression support (==, !=, +, -, *, /, &&, ||, etc.)
- Add unary expression support (!, -, +)
- Add composite literal support for struct initialization
- Add assignment to struct fields (selector on LHS)
- Add BodyStatement type to distinguish component from regular function bodies
- Add if/else statement generation in function bodies
- Move all calculator functionality to Guix files (calculator.gx)
- Use explicit return statements for regular functions

Author: claude

examples/calculator/calculator.gx

@@ -1,5 +1,15 @@
 package main
 
+import "fmt"
+import "strconv"
+
+type CalculatorState struct {
+	Display string
+	PreviousValue float64
+	Operator string
+	WaitingForOperand bool
+}
+
 func Calculator(stateChannel: chan CalculatorState) (Component) {
 	currentState := <-stateChannel
 
@@ -99,3 +109,93 @@ func Calculator(stateChannel: chan CalculatorState) (Component) {
 		}
 	}
 }
+
+func handleNumber(stateChannel: chan CalculatorState, state: CalculatorState, digit: string) {
+	if state.WaitingForOperand {
+		state.Display = digit
+		state.WaitingForOperand = false
+	} else {
+		if state.Display == "0" {
+			state.Display = digit
+		} else {
+			state.Display = state.Display + digit
+		}
+	}
+
+	stateChannel <- state
+}
+
+func handleOperator(stateChannel: chan CalculatorState, state: CalculatorState, operator: string) {
+	displayValue, _ := strconv.ParseFloat(state.Display, 64)
+
+	if state.Operator != "" && !state.WaitingForOperand {
+		result := calculate(state.PreviousValue, displayValue, state.Operator)
+		state.Display = formatNumber(result)
+		state.PreviousValue = result
+	} else {
+		state.PreviousValue = displayValue
+	}
+
+	state.WaitingForOperand = true
+	state.Operator = operator
+
+	stateChannel <- state
+}
+
+func handleEquals(stateChannel: chan CalculatorState, state: CalculatorState) {
+	if state.Operator == "" {
+		stateChannel <- state
+	} else {
+		displayValue, _ := strconv.ParseFloat(state.Display, 64)
+		result := calculate(state.PreviousValue, displayValue, state.Operator)
+
+		state.Display = formatNumber(result)
+		state.Operator = ""
+		state.WaitingForOperand = true
+		state.PreviousValue = 0
+
+		stateChannel <- state
+	}
+}
+
+func handleClear(stateChannel: chan CalculatorState) {
+	stateChannel <- CalculatorState{
+		Display: "0",
+		PreviousValue: 0,
+		Operator: "",
+		WaitingForOperand: false,
+	}
+}
+
+func calculate(a: float64, b: float64, operator: string) (float64) {
+	result := b
+	if operator == "+" {
+		result = a + b
+	} else if operator == "-" {
+		result = a - b
+	} else if operator == "*" {
+		result = a * b
+	} else if operator == "/" {
+		if b != 0 {
+			result = a / b
+		} else {
+			result = 0
+		}
+	}
+	return result
+}
+
+func formatNumber(num: float64) (string) {
+	return fmt.Sprintf("%g", num)
+}
+
+func NewCalculatorStateChannel() (chan CalculatorState) {
+	ch := make(chan CalculatorState, 10)
+	ch <- CalculatorState{
+		Display: "0",
+		PreviousValue: 0,
+		Operator: "",
+		WaitingForOperand: false,
+	}
+	return ch
+}

pkg/ast/ast.go

@@ -10,9 +10,30 @@ type File struct {
 	Pos        lexer.Position
 	Package    string       `"package" @Ident`
 	Imports    []*Import    `@@*`
+	Types      []*TypeDef   `@@*`
 	Components []*Component `@@*`
 }
 
+// TypeDef represents a type definition
+type TypeDef struct {
+	Pos    lexer.Position
+	Name   string        `"type" @Ident`
+	Struct *StructType   `@@`
+}
+
+// StructType represents a struct type definition
+type StructType struct {
+	Pos    lexer.Position
+	Fields []*StructField `"struct" "{" @@* "}"`
+}
+
+// StructField represents a field in a struct
+type StructField struct {
+	Pos  lexer.Position
+	Name string `@Ident`
+	Type *Type  `@@`
+}
+
 // Import represents an import statement
 type Import struct {
 	Pos  lexer.Position
@@ -50,12 +71,22 @@ type Type struct {
 	FuncResults []*Type
 }
 
-// Body represents a component body with optional variable declarations, assignments, and UI tree
+// Body represents a component body with optional variable declarations, statements, and UI tree
 type Body struct {
-	Pos         lexer.Position
-	VarDecls    []*VarDecl    `"{" @@*`
-	Assignments []*Assignment `@@*`
-	Children    []*Node       `@@* "}"`
+	Pos        lexer.Position
+	VarDecls   []*VarDecl       `"{" @@*`
+	Statements []*BodyStatement `@@*`
+	Children   []*Node          `@@* "}"`
+}
+
+// BodyStatement represents a statement in a component body
+type BodyStatement struct {
+	Pos        lexer.Position
+	VarDecl    *VarDecl    `@@`
+	Assignment *Assignment `| @@`
+	Return     *Return     `| @@`
+	If         *IfStmt     `| @@`
+	For        *ForLoop    `| @@`
 }
 
 // Node represents any node in the component tree
@@ -93,15 +124,54 @@ type Prop struct {
 	Value *Expr  `"(" @@ ")"`
 }
 
-// Expr represents an expression (simplified to avoid recursion)
+// Expr represents an expression with optional binary operations
 type Expr struct {
-	Pos       lexer.Position
-	Literal   *Literal      `@@`
-	MakeCall  *MakeCall     `| @@`
-	CallOrSel *CallOrSelect `| @@`
-	FuncLit   *FuncLit      `| @@`
-	ChannelOp *ChannelOp    `| @@`
-	Ident     string        `| @Ident`
+	Pos     lexer.Position
+	Left    *Primary      `@@`
+	BinOps  []*BinaryOp   `@@*`
+}
+
+// BinaryOp represents a binary operation (operator and right operand)
+type BinaryOp struct {
+	Pos   lexer.Position
+	Op    string   `@("==" | "!=" | "<=" | ">=" | "<" | ">" | "&&" | "||" | "+" | "-" | "*" | "/")`
+	Right *Primary `@@`
+}
+
+// Primary represents a primary expression (operand in binary expressions)
+type Primary struct {
+	Pos          lexer.Position
+	Unary        *UnaryExpr     `  @@`
+	Literal      *Literal       `| @@`
+	CompositeLit *CompositeLit  `| @@`
+	MakeCall     *MakeCall      `| @@`
+	CallOrSel    *CallOrSelect  `| @@`
+	FuncLit      *FuncLit       `| @@`
+	ChannelOp    *ChannelOp     `| @@`
+	Paren        *Expr          `| "(" @@ ")"`
+	Ident        string         `| @Ident`
+}
+
+// CompositeLit represents a composite literal (struct initialization)
+// Example: CalculatorState{Display: "0", PreviousValue: 0}
+type CompositeLit struct {
+	Pos      lexer.Position
+	Type     string         `@Ident`
+	Elements []*KeyValue    `"{" (@@ ("," @@)*)? ","? "}"`
+}
+
+// KeyValue represents a key-value pair in a composite literal
+type KeyValue struct {
+	Pos   lexer.Position
+	Key   string `@Ident ":"`
+	Value *Expr  `@@`
+}
+
+// UnaryExpr represents a unary expression (e.g., !x, -x)
+type UnaryExpr struct {
+	Pos   lexer.Position
+	Op    string   `@("!" | "-" | "+")`
+	Right *Primary `@@`
 }
 
 // Literal represents a literal value
@@ -167,18 +237,19 @@ type Statement struct {
 	Pos        lexer.Position
 	VarDecl    *VarDecl    `@@`
 	Assignment *Assignment `| @@`
-	Expr       *Expr       `| @@`
 	Return     *Return     `| @@`
 	If         *IfStmt     `| @@`
 	For        *ForLoop    `| @@`
+	Expr       *Expr       `| @@`
 }
 
 // Assignment represents an assignment statement
 type Assignment struct {
-	Pos   lexer.Position
-	Left  string `@Ident`
-	Op    string `@("<-" | ":=" | "=" | "+=" | "-=" | "*=" | "/=")`
-	Right *Expr  `@@`
+	Pos          lexer.Position
+	Left         string   `@Ident`
+	LeftSelector []string `("." @Ident)*`
+	Op           string   `@("<-" | ":=" | "=" | "+=" | "-=" | "*=" | "/=")`
+	Right        *Expr    `@@`
 }
 
 // Return represents a return statement