package main

// Node represents an AST node.
type Node interface {
	isNode()
}

type Expr interface {
	Node
	isExpr()
}

// BinaryExpr represents a binary operation.
type BinaryExpr struct {
	Op    string
	Left  Expr
	Right Expr
}

func (e *BinaryExpr) isNode() {}
func (e *BinaryExpr) isExpr() {}

// UnaryExpr represents a unary operation (+, -, ~).
type UnaryExpr struct {
	Op   string
	Expr Expr
}

func (e *UnaryExpr) isNode() {}
func (e *UnaryExpr) isExpr() {}

// NumberExpr represents a numeric literal.
type NumberExpr struct {
	Value string // parsed as decimal later
}

func (e *NumberExpr) isNode() {}
func (e *NumberExpr) isExpr() {}

// IdentExpr represents an identifier (variable, unit, constant, or currency symbol).
type IdentExpr struct {
	Name string
}

func (e *IdentExpr) isNode() {}
func (e *IdentExpr) isExpr() {}

// CallExpr represents a function call.
type CallExpr struct {
	Func string
	Args []Expr
}

func (e *CallExpr) isNode() {}
func (e *CallExpr) isExpr() {}

// StringExpr represents a string literal.
type StringExpr struct {
	Value string
}

func (e *StringExpr) isNode() {}
func (e *StringExpr) isExpr() {}