monkey/ast/ast.go

package ast

import (
	"bytes"
	"monkey/token"
)

type Node interface {
	TokenLiteral() string
	String() string
}

type Statement interface {
	Node
	statementNode()
}

type Expression interface {
	Node
	expressionNode()
}

type Program struct {
	Statements []Statement
}

func (p *Program) TokenLiteral() string {
	if len(p.Statements) > 0 {
		return p.Statements[0].TokenLiteral()
	} else {
		return ""
	}
}

func (p *Program) String() string {
	var out bytes.Buffer

	for _, s := range p.Statements {
		out.WriteString(s.String())
	}

	return out.String()
}

type Identifier struct {
	Token token.Token // the token.Ident token
	Value string
}

type LetStatement struct {
	Token token.Token // the token.Let token
	Name  *Identifier
	Value Expression
}

type ReturnStatement struct {
	Token       token.Token // the 'return token
	ReturnValue Expression
}

type ExpressionStatement struct {
	Token      token.Token // the first token of the expression
	Expression Expression
}

type IntegerLiteral struct {
	Token token.Token
	Value int64
}

type PrefixExpression struct {
	Token    token.Token
	Operator string
	Right    Expression
}

type InfixExpression struct {
	Token    token.Token
	Left     Expression
	Operator string
	Right    Expression
}

type Boolean struct {
	Token token.Token
	Value bool
}

type BlockStatement struct {
	Token      token.Token // the { token
	Statements []Statement
}

type IfExpression struct {
	Token       token.Token // The 'if' token
	Condition   Expression
	Consequence *BlockStatement
	Alternative *BlockStatement
}

func (ls *LetStatement) statementNode() {
}
func (ls *LetStatement) TokenLiteral() string {
	return ls.Token.Literal
}
func (ls *LetStatement) String() string {
	var out bytes.Buffer

	out.WriteString(ls.TokenLiteral() + " ")
	out.WriteString(ls.Name.String())
	out.WriteString(" = ")

	if ls.Value != nil {
		out.WriteString(ls.Value.String())
	}

	out.WriteString(";")

	return out.String()
}

func (i *Identifier) expressionNode() {
}
func (i *Identifier) TokenLiteral() string {
	return i.Token.Literal
}
func (i *Identifier) String() string { return i.Value }

func (rs *ReturnStatement) statementNode() {
}
func (rs *ReturnStatement) TokenLiteral() string {
	return rs.Token.Literal
}
func (rs *ReturnStatement) String() string {
	var out bytes.Buffer

	out.WriteString(rs.TokenLiteral() + " ")

	if rs.ReturnValue != nil {
		out.WriteString(rs.ReturnValue.String())
	}

	out.WriteString(";")

	return out.String()
}

func (es *ExpressionStatement) statementNode() {
}
func (es *ExpressionStatement) TokenLiteral() string {
	return es.Token.Literal
}
func (es *ExpressionStatement) String() string {
	if es.Expression != nil {
		return es.Expression.String()
	}

	return ""
}

func (il *IntegerLiteral) expressionNode() {
}
func (il *IntegerLiteral) TokenLiteral() string {
	return il.Token.Literal
}
func (il *IntegerLiteral) String() string {
	return il.Token.Literal
}

func (pe *PrefixExpression) expressionNode() {}
func (pe *PrefixExpression) TokenLiteral() string {
	return pe.Token.Literal
}
func (pe *PrefixExpression) String() string {
	var out bytes.Buffer

	out.WriteString("(")
	out.WriteString(pe.Operator)
	out.WriteString(pe.Right.String())
	out.WriteString(")")

	return out.String()
}

func (ie *InfixExpression) expressionNode() {}
func (ie *InfixExpression) TokenLiteral() string {
	return ie.Token.Literal
}
func (ie *InfixExpression) String() string {
	var out bytes.Buffer

	out.WriteString("(")
	out.WriteString(ie.Left.String())
	out.WriteString(" " + ie.Operator + " ")
	out.WriteString(ie.Right.String())
	out.WriteString(")")

	return out.String()
}

func (b Boolean) TokenLiteral() string {
	return b.Token.Literal
}
func (b Boolean) String() string {
	return b.Token.Literal
}
func (b Boolean) expressionNode() {}

func (bs BlockStatement) TokenLiteral() string {
	return bs.Token.Literal
}
func (bs BlockStatement) String() string {
	var out bytes.Buffer

	for _, s := range bs.Statements {
		out.WriteString(s.String())
	}

	return out.String()
}
func (bs BlockStatement) statementNode() {}

func (ie IfExpression) TokenLiteral() string {
	return ie.Token.Literal
}
func (ie IfExpression) String() string {
	var out bytes.Buffer

	out.WriteString("if")
	out.WriteString(ie.Condition.String())
	out.WriteString(" ")
	out.WriteString(ie.Consequence.String())

	if ie.Alternative != nil {
		out.WriteString("else ")
		out.WriteString(ie.Alternative.String())
	}

	return out.String()
}
func (ie IfExpression) expressionNode() {}