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ast.go
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ast.go
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package ast
import (
"bytes"
"monkey/token"
"strings"
)
// The base Node interface
type Node interface {
TokenLiteral() string
String() string
}
// All statement nodes implement this
type Statement interface {
Node
statementNode()
}
// All expression nodes implement this
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()
}
// Statements
type LetStatement struct {
Token token.Token // the token.LET token
Name *Identifier
Value Expression
}
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()
}
type ReturnStatement struct {
Token token.Token // the 'return' token
ReturnValue Expression
}
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()
}
type ExpressionStatement struct {
Token token.Token // the first token of the expression
Expression Expression
}
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 ""
}
type BlockStatement struct {
Token token.Token // the { token
Statements []Statement
}
func (bs *BlockStatement) statementNode() {}
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()
}
// Expressions
type Identifier struct {
Token token.Token // the token.IDENT token
Value string
}
func (i *Identifier) expressionNode() {}
func (i *Identifier) TokenLiteral() string { return i.Token.Literal }
func (i *Identifier) String() string { return i.Value }
type Boolean struct {
Token token.Token
Value bool
}
func (b *Boolean) expressionNode() {}
func (b *Boolean) TokenLiteral() string { return b.Token.Literal }
func (b *Boolean) String() string { return b.Token.Literal }
type IntegerLiteral struct {
Token token.Token
Value int64
}
func (il *IntegerLiteral) expressionNode() {}
func (il *IntegerLiteral) TokenLiteral() string { return il.Token.Literal }
func (il *IntegerLiteral) String() string { return il.Token.Literal }
type PrefixExpression struct {
Token token.Token // The prefix token, e.g. !
Operator string
Right Expression
}
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()
}
type InfixExpression struct {
Token token.Token // The operator token, e.g. +
Left Expression
Operator string
Right Expression
}
func (oe *InfixExpression) expressionNode() {}
func (oe *InfixExpression) TokenLiteral() string { return oe.Token.Literal }
func (oe *InfixExpression) String() string {
var out bytes.Buffer
out.WriteString("(")
out.WriteString(oe.Left.String())
out.WriteString(" " + oe.Operator + " ")
out.WriteString(oe.Right.String())
out.WriteString(")")
return out.String()
}
type IfExpression struct {
Token token.Token // The 'if' token
Condition Expression
Consequence *BlockStatement
Alternative *BlockStatement
}
func (ie *IfExpression) expressionNode() {}
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()
}
type FunctionLiteral struct {
Token token.Token // The 'fn' token
Parameters []*Identifier
Body *BlockStatement
}
func (fl *FunctionLiteral) expressionNode() {}
func (fl *FunctionLiteral) TokenLiteral() string { return fl.Token.Literal }
func (fl *FunctionLiteral) String() string {
var out bytes.Buffer
params := []string{}
for _, p := range fl.Parameters {
params = append(params, p.String())
}
out.WriteString(fl.TokenLiteral())
out.WriteString("(")
out.WriteString(strings.Join(params, ", "))
out.WriteString(") ")
out.WriteString(fl.Body.String())
return out.String()
}
type CallExpression struct {
Token token.Token // The '(' token
Function Expression // Identifier or FunctionLiteral
Arguments []Expression
}
func (ce *CallExpression) expressionNode() {}
func (ce *CallExpression) TokenLiteral() string { return ce.Token.Literal }
func (ce *CallExpression) String() string {
var out bytes.Buffer
args := []string{}
for _, a := range ce.Arguments {
args = append(args, a.String())
}
out.WriteString(ce.Function.String())
out.WriteString("(")
out.WriteString(strings.Join(args, ", "))
out.WriteString(")")
return out.String()
}
type StringLiteral struct {
Token token.Token
Value string
}
func (sl *StringLiteral) expressionNode() {}
func (sl *StringLiteral) TokenLiteral() string { return sl.Token.Literal }
func (sl *StringLiteral) String() string { return sl.Token.Literal }
type ArrayLiteral struct {
Token token.Token // the '[' token
Elements []Expression
}
func (al *ArrayLiteral) expressionNode() {}
func (al *ArrayLiteral) TokenLiteral() string { return al.Token.Literal }
func (al *ArrayLiteral) String() string {
var out bytes.Buffer
elements := []string{}
for _, el := range al.Elements {
elements = append(elements, el.String())
}
out.WriteString("[")
out.WriteString(strings.Join(elements, ", "))
out.WriteString("]")
return out.String()
}
type IndexExpression struct {
Token token.Token // The [ token
Left Expression
Index Expression
}
func (ie *IndexExpression) expressionNode() {}
func (ie *IndexExpression) TokenLiteral() string { return ie.Token.Literal }
func (ie *IndexExpression) String() string {
var out bytes.Buffer
out.WriteString("(")
out.WriteString(ie.Left.String())
out.WriteString("[")
out.WriteString(ie.Index.String())
out.WriteString("])")
return out.String()
}
type HashLiteral struct {
Token token.Token // the '{' token
Pairs map[Expression]Expression
}
func (hl *HashLiteral) expressionNode() {}
func (hl *HashLiteral) TokenLiteral() string { return hl.Token.Literal }
func (hl *HashLiteral) String() string {
var out bytes.Buffer
pairs := []string{}
for key, value := range hl.Pairs {
pairs = append(pairs, key.String()+":"+value.String())
}
out.WriteString("{")
out.WriteString(strings.Join(pairs, ", "))
out.WriteString("}")
return out.String()
}