Started chapter 2 on Parsers

.gitignore

@@ -1,3 +1,5 @@
+.DS_Store
+
 # ---> Go
 # If you prefer the allow list template instead of the deny list, see community template:
 # https://github.com/github/gitignore/blob/main/community/Golang/Go.AllowList.gitignore

monkey2/ast/ast.go

@@ -0,0 +1,267 @@
+package ast
+
+import (
+	"bytes"
+	"strings"
+
+	"gitea.paas.celticinfo.fr/oabrivard/monkeylang/monkey2/token"
+)
+
+// 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()
+}

monkey2/ast/ast_test.go

@@ -0,0 +1,29 @@
+package ast
+
+import (
+	"testing"
+
+	"gitea.paas.celticinfo.fr/oabrivard/monkeylang/monkey2/token"
+)
+
+func TestString(t *testing.T) {
+	program := &Program{
+		Statements: []Statement{
+			&LetStatement{
+				Token: token.Token{Type: token.LET, Literal: "let"},
+				Name: &Identifier{
+					Token: token.Token{Type: token.IDENT, Literal: "myVar"},
+					Value: "myVar",
+				},
+				Value: &Identifier{
+					Token: token.Token{Type: token.IDENT, Literal: "anotherVar"},
+					Value: "anotherVar",
+				},
+			},
+		},
+	}
+
+	if program.String() != "let myVar = anotherVar;" {
+		t.Errorf("program.String() wrong. got=%q", program.String())
+	}
+}

monkey2/lexer/lexer.go

@@ -0,0 +1,137 @@
+package lexer
+
+import "gitea.paas.celticinfo.fr/oabrivard/monkeylang/monkey2/token"
+
+type Lexer struct {
+	input        string
+	position     int  // current position in input (points to current char)
+	readPosition int  // current reading position in input (after current char)
+	ch           byte // current char under examination
+}
+
+func New(input string) *Lexer {
+	l := &Lexer{input: input}
+	l.readChar()
+	return l
+}
+
+func (l *Lexer) NextToken() token.Token {
+	var tok token.Token
+
+	l.skipWhitespace()
+
+	switch l.ch {
+	case '=':
+		if l.peekChar() == '=' {
+			ch := l.ch
+			l.readChar()
+			literal := string(ch) + string(l.ch)
+			tok = token.Token{Type: token.EQ, Literal: literal}
+		} else {
+			tok = newToken(token.ASSIGN, l.ch)
+		}
+	case '+':
+		tok = newToken(token.PLUS, l.ch)
+	case '-':
+		tok = newToken(token.MINUS, l.ch)
+	case '!':
+		if l.peekChar() == '=' {
+			ch := l.ch
+			l.readChar()
+			literal := string(ch) + string(l.ch)
+			tok = token.Token{Type: token.NOT_EQ, Literal: literal}
+		} else {
+			tok = newToken(token.BANG, l.ch)
+		}
+	case '/':
+		tok = newToken(token.SLASH, l.ch)
+	case '*':
+		tok = newToken(token.ASTERISK, l.ch)
+	case '<':
+		tok = newToken(token.LT, l.ch)
+	case '>':
+		tok = newToken(token.GT, l.ch)
+	case ';':
+		tok = newToken(token.SEMICOLON, l.ch)
+	case ',':
+		tok = newToken(token.COMMA, l.ch)
+	case '{':
+		tok = newToken(token.LBRACE, l.ch)
+	case '}':
+		tok = newToken(token.RBRACE, l.ch)
+	case '(':
+		tok = newToken(token.LPAREN, l.ch)
+	case ')':
+		tok = newToken(token.RPAREN, l.ch)
+	case 0:
+		tok.Literal = ""
+		tok.Type = token.EOF
+	default:
+		if isLetter(l.ch) {
+			tok.Literal = l.readIdentifier()
+			tok.Type = token.LookupIdent(tok.Literal)
+			return tok
+		} else if isDigit(l.ch) {
+			tok.Type = token.INT
+			tok.Literal = l.readNumber()
+			return tok
+		} else {
+			tok = newToken(token.ILLEGAL, l.ch)
+		}
+	}
+
+	l.readChar()
+	return tok
+}
+
+func (l *Lexer) skipWhitespace() {
+	for l.ch == ' ' || l.ch == '\t' || l.ch == '\n' || l.ch == '\r' {
+		l.readChar()
+	}
+}
+
+func (l *Lexer) readChar() {
+	if l.readPosition >= len(l.input) {
+		l.ch = 0
+	} else {
+		l.ch = l.input[l.readPosition]
+	}
+	l.position = l.readPosition
+	l.readPosition += 1
+}
+
+func (l *Lexer) peekChar() byte {
+	if l.readPosition >= len(l.input) {
+		return 0
+	} else {
+		return l.input[l.readPosition]
+	}
+}
+
+func (l *Lexer) readIdentifier() string {
+	position := l.position
+	for isLetter(l.ch) {
+		l.readChar()
+	}
+	return l.input[position:l.position]
+}
+
+func (l *Lexer) readNumber() string {
+	position := l.position
+	for isDigit(l.ch) {
+		l.readChar()
+	}
+	return l.input[position:l.position]
+}
+
+func isLetter(ch byte) bool {
+	return 'a' <= ch && ch <= 'z' || 'A' <= ch && ch <= 'Z' || ch == '_'
+}
+
+func isDigit(ch byte) bool {
+	return '0' <= ch && ch <= '9'
+}
+
+func newToken(tokenType token.TokenType, ch byte) token.Token {
+	return token.Token{Type: tokenType, Literal: string(ch)}
+}

monkey2/lexer/lexer_test.go

@@ -0,0 +1,126 @@
+package lexer
+
+import (
+	"testing"
+
+	"gitea.paas.celticinfo.fr/oabrivard/monkeylang/monkey2/token"
+)
+
+func TestNextToken(t *testing.T) {
+	input := `let five = 5;
+let ten = 10;
+
+let add = fn(x, y) {
+  x + y;
+};
+
+let result = add(five, ten);
+!-/*5;
+5 < 10 > 5;
+
+if (5 < 10) {
+	return true;
+} else {
+	return false;
+}
+
+10 == 10;
+10 != 9;
+`
+
+	tests := []struct {
+		expectedType    token.TokenType
+		expectedLiteral string
+	}{
+		{token.LET, "let"},
+		{token.IDENT, "five"},
+		{token.ASSIGN, "="},
+		{token.INT, "5"},
+		{token.SEMICOLON, ";"},
+		{token.LET, "let"},
+		{token.IDENT, "ten"},
+		{token.ASSIGN, "="},
+		{token.INT, "10"},
+		{token.SEMICOLON, ";"},
+		{token.LET, "let"},
+		{token.IDENT, "add"},
+		{token.ASSIGN, "="},
+		{token.FUNCTION, "fn"},
+		{token.LPAREN, "("},
+		{token.IDENT, "x"},
+		{token.COMMA, ","},
+		{token.IDENT, "y"},
+		{token.RPAREN, ")"},
+		{token.LBRACE, "{"},
+		{token.IDENT, "x"},
+		{token.PLUS, "+"},
+		{token.IDENT, "y"},
+		{token.SEMICOLON, ";"},
+		{token.RBRACE, "}"},
+		{token.SEMICOLON, ";"},
+		{token.LET, "let"},
+		{token.IDENT, "result"},
+		{token.ASSIGN, "="},
+		{token.IDENT, "add"},
+		{token.LPAREN, "("},
+		{token.IDENT, "five"},
+		{token.COMMA, ","},
+		{token.IDENT, "ten"},
+		{token.RPAREN, ")"},
+		{token.SEMICOLON, ";"},
+		{token.BANG, "!"},
+		{token.MINUS, "-"},
+		{token.SLASH, "/"},
+		{token.ASTERISK, "*"},
+		{token.INT, "5"},
+		{token.SEMICOLON, ";"},
+		{token.INT, "5"},
+		{token.LT, "<"},
+		{token.INT, "10"},
+		{token.GT, ">"},
+		{token.INT, "5"},
+		{token.SEMICOLON, ";"},
+		{token.IF, "if"},
+		{token.LPAREN, "("},
+		{token.INT, "5"},
+		{token.LT, "<"},
+		{token.INT, "10"},
+		{token.RPAREN, ")"},
+		{token.LBRACE, "{"},
+		{token.RETURN, "return"},
+		{token.TRUE, "true"},
+		{token.SEMICOLON, ";"},
+		{token.RBRACE, "}"},
+		{token.ELSE, "else"},
+		{token.LBRACE, "{"},
+		{token.RETURN, "return"},
+		{token.FALSE, "false"},
+		{token.SEMICOLON, ";"},
+		{token.RBRACE, "}"},
+		{token.INT, "10"},
+		{token.EQ, "=="},
+		{token.INT, "10"},
+		{token.SEMICOLON, ";"},
+		{token.INT, "10"},
+		{token.NOT_EQ, "!="},
+		{token.INT, "9"},
+		{token.SEMICOLON, ";"},
+		{token.EOF, ""},
+	}
+
+	l := New(input)
+
+	for i, tt := range tests {
+		tok := l.NextToken()
+
+		if tok.Type != tt.expectedType {
+			t.Fatalf("tests[%d] - tokentype wrong. expected=%q, got=%q",
+				i, tt.expectedType, tok.Type)
+		}
+
+		if tok.Literal != tt.expectedLiteral {
+			t.Fatalf("tests[%d] - literal wrong. expected=%q, got=%q",
+				i, tt.expectedLiteral, tok.Literal)
+		}
+	}
+}

monkey2/main.go

@@ -0,0 +1,20 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"os/user"
+
+	"gitea.paas.celticinfo.fr/oabrivard/monkeylang/monkey2/repl"
+)
+
+func main() {
+	user, err := user.Current()
+	if err != nil {
+		panic(err)
+	}
+	fmt.Printf("Hello %s! This is the Monkey programming language!\n",
+		user.Username)
+	fmt.Printf("Feel free to type in commands\n")
+	repl.Start(os.Stdin, os.Stdout)
+}

monkey2/parser/parser.go

@@ -0,0 +1,432 @@
+package parser
+
+import (
+	"fmt"
+	"strconv"
+
+	"gitea.paas.celticinfo.fr/oabrivard/monkeylang/monkey2/ast"
+	"gitea.paas.celticinfo.fr/oabrivard/monkeylang/monkey2/lexer"
+	"gitea.paas.celticinfo.fr/oabrivard/monkeylang/monkey2/token"
+)
+
+const (
+	_ int = iota
+	LOWEST
+	EQUALS      // ==
+	LESSGREATER // > or <
+	SUM         // +
+	PRODUCT     // *
+	PREFIX      // -X or !X
+	CALL        // myFunction(X)
+)
+
+var precedences = map[token.TokenType]int{
+	token.EQ:       EQUALS,
+	token.NOT_EQ:   EQUALS,
+	token.LT:       LESSGREATER,
+	token.GT:       LESSGREATER,
+	token.PLUS:     SUM,
+	token.MINUS:    SUM,
+	token.SLASH:    PRODUCT,
+	token.ASTERISK: PRODUCT,
+	token.LPAREN:   CALL,
+}
+
+type (
+	prefixParseFn func() ast.Expression
+	infixParseFn  func(ast.Expression) ast.Expression
+)
+
+type Parser struct {
+	l      *lexer.Lexer
+	errors []string
+
+	curToken  token.Token
+	peekToken token.Token
+
+	prefixParseFns map[token.TokenType]prefixParseFn
+	infixParseFns  map[token.TokenType]infixParseFn
+}
+
+func New(l *lexer.Lexer) *Parser {
+	p := &Parser{
+		l:      l,
+		errors: []string{},
+	}
+
+	p.prefixParseFns = make(map[token.TokenType]prefixParseFn)
+	p.registerPrefix(token.IDENT, p.parseIdentifier)
+	p.registerPrefix(token.INT, p.parseIntegerLiteral)
+	p.registerPrefix(token.BANG, p.parsePrefixExpression)
+	p.registerPrefix(token.MINUS, p.parsePrefixExpression)
+	p.registerPrefix(token.TRUE, p.parseBoolean)
+	p.registerPrefix(token.FALSE, p.parseBoolean)
+	p.registerPrefix(token.LPAREN, p.parseGroupedExpression)
+	p.registerPrefix(token.IF, p.parseIfExpression)
+	p.registerPrefix(token.FUNCTION, p.parseFunctionLiteral)
+
+	p.infixParseFns = make(map[token.TokenType]infixParseFn)
+	p.registerInfix(token.PLUS, p.parseInfixExpression)
+	p.registerInfix(token.MINUS, p.parseInfixExpression)
+	p.registerInfix(token.SLASH, p.parseInfixExpression)
+	p.registerInfix(token.ASTERISK, p.parseInfixExpression)
+	p.registerInfix(token.EQ, p.parseInfixExpression)
+	p.registerInfix(token.NOT_EQ, p.parseInfixExpression)
+	p.registerInfix(token.LT, p.parseInfixExpression)
+	p.registerInfix(token.GT, p.parseInfixExpression)
+
+	p.registerInfix(token.LPAREN, p.parseCallExpression)
+
+	// Read two tokens, so curToken and peekToken are both set
+	p.nextToken()
+	p.nextToken()
+
+	return p
+}
+
+func (p *Parser) nextToken() {
+	p.curToken = p.peekToken
+	p.peekToken = p.l.NextToken()
+}
+
+func (p *Parser) curTokenIs(t token.TokenType) bool {
+	return p.curToken.Type == t
+}
+
+func (p *Parser) peekTokenIs(t token.TokenType) bool {
+	return p.peekToken.Type == t
+}
+
+func (p *Parser) expectPeek(t token.TokenType) bool {
+	if p.peekTokenIs(t) {
+		p.nextToken()
+		return true
+	} else {
+		p.peekError(t)
+		return false
+	}
+}
+
+func (p *Parser) Errors() []string {
+	return p.errors
+}
+
+func (p *Parser) peekError(t token.TokenType) {
+	msg := fmt.Sprintf("expected next token to be %s, got %s instead",
+		t, p.peekToken.Type)
+	p.errors = append(p.errors, msg)
+}
+
+func (p *Parser) noPrefixParseFnError(t token.TokenType) {
+	msg := fmt.Sprintf("no prefix parse function for %s found", t)
+	p.errors = append(p.errors, msg)
+}
+
+func (p *Parser) ParseProgram() *ast.Program {
+	program := &ast.Program{}
+	program.Statements = []ast.Statement{}
+
+	for !p.curTokenIs(token.EOF) {
+		stmt := p.parseStatement()
+		if stmt != nil {
+			program.Statements = append(program.Statements, stmt)
+		}
+		p.nextToken()
+	}
+
+	return program
+}
+
+func (p *Parser) parseStatement() ast.Statement {
+	switch p.curToken.Type {
+	case token.LET:
+		return p.parseLetStatement()
+	case token.RETURN:
+		return p.parseReturnStatement()
+	default:
+		return p.parseExpressionStatement()
+	}
+}
+
+func (p *Parser) parseLetStatement() *ast.LetStatement {
+	stmt := &ast.LetStatement{Token: p.curToken}
+
+	if !p.expectPeek(token.IDENT) {
+		return nil
+	}
+
+	stmt.Name = &ast.Identifier{Token: p.curToken, Value: p.curToken.Literal}
+
+	if !p.expectPeek(token.ASSIGN) {
+		return nil
+	}
+
+	p.nextToken()
+
+	stmt.Value = p.parseExpression(LOWEST)
+
+	if p.peekTokenIs(token.SEMICOLON) {
+		p.nextToken()
+	}
+
+	return stmt
+}
+
+func (p *Parser) parseReturnStatement() *ast.ReturnStatement {
+	stmt := &ast.ReturnStatement{Token: p.curToken}
+
+	p.nextToken()
+
+	stmt.ReturnValue = p.parseExpression(LOWEST)
+
+	if p.peekTokenIs(token.SEMICOLON) {
+		p.nextToken()
+	}
+
+	return stmt
+}
+
+func (p *Parser) parseExpressionStatement() *ast.ExpressionStatement {
+	stmt := &ast.ExpressionStatement{Token: p.curToken}
+
+	stmt.Expression = p.parseExpression(LOWEST)
+
+	if p.peekTokenIs(token.SEMICOLON) {
+		p.nextToken()
+	}
+
+	return stmt
+}
+
+func (p *Parser) parseExpression(precedence int) ast.Expression {
+	prefix := p.prefixParseFns[p.curToken.Type]
+	if prefix == nil {
+		p.noPrefixParseFnError(p.curToken.Type)
+		return nil
+	}
+	leftExp := prefix()
+
+	for !p.peekTokenIs(token.SEMICOLON) && precedence < p.peekPrecedence() {
+		infix := p.infixParseFns[p.peekToken.Type]
+		if infix == nil {
+			return leftExp
+		}
+
+		p.nextToken()
+
+		leftExp = infix(leftExp)
+	}
+
+	return leftExp
+}
+
+func (p *Parser) peekPrecedence() int {
+	if p, ok := precedences[p.peekToken.Type]; ok {
+		return p
+	}
+
+	return LOWEST
+}
+
+func (p *Parser) curPrecedence() int {
+	if p, ok := precedences[p.curToken.Type]; ok {
+		return p
+	}
+
+	return LOWEST
+}
+
+func (p *Parser) parseIdentifier() ast.Expression {
+	return &ast.Identifier{Token: p.curToken, Value: p.curToken.Literal}
+}
+
+func (p *Parser) parseIntegerLiteral() ast.Expression {
+	lit := &ast.IntegerLiteral{Token: p.curToken}
+
+	value, err := strconv.ParseInt(p.curToken.Literal, 0, 64)
+	if err != nil {
+		msg := fmt.Sprintf("could not parse %q as integer", p.curToken.Literal)
+		p.errors = append(p.errors, msg)
+		return nil
+	}
+
+	lit.Value = value
+
+	return lit
+}
+
+func (p *Parser) parsePrefixExpression() ast.Expression {
+	expression := &ast.PrefixExpression{
+		Token:    p.curToken,
+		Operator: p.curToken.Literal,
+	}
+
+	p.nextToken()
+
+	expression.Right = p.parseExpression(PREFIX)
+
+	return expression
+}
+
+func (p *Parser) parseInfixExpression(left ast.Expression) ast.Expression {
+	expression := &ast.InfixExpression{
+		Token:    p.curToken,
+		Operator: p.curToken.Literal,
+		Left:     left,
+	}
+
+	precedence := p.curPrecedence()
+	p.nextToken()
+	expression.Right = p.parseExpression(precedence)
+
+	return expression
+}
+
+func (p *Parser) parseBoolean() ast.Expression {
+	return &ast.Boolean{Token: p.curToken, Value: p.curTokenIs(token.TRUE)}
+}
+
+func (p *Parser) parseGroupedExpression() ast.Expression {
+	p.nextToken()
+
+	exp := p.parseExpression(LOWEST)
+
+	if !p.expectPeek(token.RPAREN) {
+		return nil
+	}
+
+	return exp
+}
+
+func (p *Parser) parseIfExpression() ast.Expression {
+	expression := &ast.IfExpression{Token: p.curToken}
+
+	if !p.expectPeek(token.LPAREN) {
+		return nil
+	}
+
+	p.nextToken()
+	expression.Condition = p.parseExpression(LOWEST)
+
+	if !p.expectPeek(token.RPAREN) {
+		return nil
+	}
+
+	if !p.expectPeek(token.LBRACE) {
+		return nil
+	}
+
+	expression.Consequence = p.parseBlockStatement()
+
+	if p.peekTokenIs(token.ELSE) {
+		p.nextToken()
+
+		if !p.expectPeek(token.LBRACE) {
+			return nil
+		}
+
+		expression.Alternative = p.parseBlockStatement()
+	}
+
+	return expression
+}
+
+func (p *Parser) parseBlockStatement() *ast.BlockStatement {
+	block := &ast.BlockStatement{Token: p.curToken}
+	block.Statements = []ast.Statement{}
+
+	p.nextToken()
+
+	for !p.curTokenIs(token.RBRACE) && !p.curTokenIs(token.EOF) {
+		stmt := p.parseStatement()
+		if stmt != nil {
+			block.Statements = append(block.Statements, stmt)
+		}
+		p.nextToken()
+	}
+
+	return block
+}
+
+func (p *Parser) parseFunctionLiteral() ast.Expression {
+	lit := &ast.FunctionLiteral{Token: p.curToken}
+
+	if !p.expectPeek(token.LPAREN) {
+		return nil
+	}
+
+	lit.Parameters = p.parseFunctionParameters()
+
+	if !p.expectPeek(token.LBRACE) {
+		return nil
+	}
+
+	lit.Body = p.parseBlockStatement()
+
+	return lit
+}
+
+func (p *Parser) parseFunctionParameters() []*ast.Identifier {
+	identifiers := []*ast.Identifier{}
+
+	if p.peekTokenIs(token.RPAREN) {
+		p.nextToken()
+		return identifiers
+	}
+
+	p.nextToken()
+
+	ident := &ast.Identifier{Token: p.curToken, Value: p.curToken.Literal}
+	identifiers = append(identifiers, ident)
+
+	for p.peekTokenIs(token.COMMA) {
+		p.nextToken()
+		p.nextToken()
+		ident := &ast.Identifier{Token: p.curToken, Value: p.curToken.Literal}
+		identifiers = append(identifiers, ident)
+	}
+
+	if !p.expectPeek(token.RPAREN) {
+		return nil
+	}
+
+	return identifiers
+}
+
+func (p *Parser) parseCallExpression(function ast.Expression) ast.Expression {
+	exp := &ast.CallExpression{Token: p.curToken, Function: function}
+	exp.Arguments = p.parseCallArguments()
+	return exp
+}
+
+func (p *Parser) parseCallArguments() []ast.Expression {
+	args := []ast.Expression{}
+
+	if p.peekTokenIs(token.RPAREN) {
+		p.nextToken()
+		return args
+	}
+
+	p.nextToken()
+	args = append(args, p.parseExpression(LOWEST))
+
+	for p.peekTokenIs(token.COMMA) {
+		p.nextToken()
+		p.nextToken()
+		args = append(args, p.parseExpression(LOWEST))
+	}
+
+	if !p.expectPeek(token.RPAREN) {
+		return nil
+	}
+
+	return args
+}
+
+func (p *Parser) registerPrefix(tokenType token.TokenType, fn prefixParseFn) {
+	p.prefixParseFns[tokenType] = fn
+}
+
+func (p *Parser) registerInfix(tokenType token.TokenType, fn infixParseFn) {
+	p.infixParseFns[tokenType] = fn
+}

monkey2/parser/parser_test.go

@@ -0,0 +1,817 @@
+package parser
+
+import (
+	"fmt"
+	"testing"
+
+	"gitea.paas.celticinfo.fr/oabrivard/monkeylang/monkey2/ast"
+	"gitea.paas.celticinfo.fr/oabrivard/monkeylang/monkey2/lexer"
+)
+
+func TestLetStatements(t *testing.T) {
+	tests := []struct {
+		input              string
+		expectedIdentifier string
+		expectedValue      interface{}
+	}{
+		{"let x = 5;", "x", 5},
+		{"let y = true;", "y", true},
+		{"let foobar = y;", "foobar", "y"},
+	}
+
+	for _, tt := range tests {
+		l := lexer.New(tt.input)
+		p := New(l)
+		program := p.ParseProgram()
+		checkParserErrors(t, p)
+
+		if len(program.Statements) != 1 {
+			t.Fatalf("program.Statements does not contain 1 statements. got=%d",
+				len(program.Statements))
+		}
+
+		stmt := program.Statements[0]
+		if !testLetStatement(t, stmt, tt.expectedIdentifier) {
+			return
+		}
+
+		val := stmt.(*ast.LetStatement).Value
+		if !testLiteralExpression(t, val, tt.expectedValue) {
+			return
+		}
+	}
+}
+
+func TestReturnStatements(t *testing.T) {
+	tests := []struct {
+		input         string
+		expectedValue interface{}
+	}{
+		{"return 5;", 5},
+		{"return true;", true},
+		{"return foobar;", "foobar"},
+	}
+
+	for _, tt := range tests {
+		l := lexer.New(tt.input)
+		p := New(l)
+		program := p.ParseProgram()
+		checkParserErrors(t, p)
+
+		if len(program.Statements) != 1 {
+			t.Fatalf("program.Statements does not contain 1 statements. got=%d",
+				len(program.Statements))
+		}
+
+		stmt := program.Statements[0]
+		returnStmt, ok := stmt.(*ast.ReturnStatement)
+		if !ok {
+			t.Fatalf("stmt not *ast.returnStatement. got=%T", stmt)
+		}
+		if returnStmt.TokenLiteral() != "return" {
+			t.Fatalf("returnStmt.TokenLiteral not 'return', got %q",
+				returnStmt.TokenLiteral())
+		}
+		if testLiteralExpression(t, returnStmt.ReturnValue, tt.expectedValue) {
+			return
+		}
+	}
+}
+
+func TestIdentifierExpression(t *testing.T) {
+	input := "foobar;"
+
+	l := lexer.New(input)
+	p := New(l)
+	program := p.ParseProgram()
+	checkParserErrors(t, p)
+
+	if len(program.Statements) != 1 {
+		t.Fatalf("program has not enough statements. got=%d",
+			len(program.Statements))
+	}
+	stmt, ok := program.Statements[0].(*ast.ExpressionStatement)
+	if !ok {
+		t.Fatalf("program.Statements[0] is not ast.ExpressionStatement. got=%T",
+			program.Statements[0])
+	}
+
+	ident, ok := stmt.Expression.(*ast.Identifier)
+	if !ok {
+		t.Fatalf("exp not *ast.Identifier. got=%T", stmt.Expression)
+	}
+	if ident.Value != "foobar" {
+		t.Errorf("ident.Value not %s. got=%s", "foobar", ident.Value)
+	}
+	if ident.TokenLiteral() != "foobar" {
+		t.Errorf("ident.TokenLiteral not %s. got=%s", "foobar",
+			ident.TokenLiteral())
+	}
+}
+
+func TestIntegerLiteralExpression(t *testing.T) {
+	input := "5;"
+
+	l := lexer.New(input)
+	p := New(l)
+	program := p.ParseProgram()
+	checkParserErrors(t, p)
+
+	if len(program.Statements) != 1 {
+		t.Fatalf("program has not enough statements. got=%d",
+			len(program.Statements))
+	}
+	stmt, ok := program.Statements[0].(*ast.ExpressionStatement)
+	if !ok {
+		t.Fatalf("program.Statements[0] is not ast.ExpressionStatement. got=%T",
+			program.Statements[0])
+	}
+
+	literal, ok := stmt.Expression.(*ast.IntegerLiteral)
+	if !ok {
+		t.Fatalf("exp not *ast.IntegerLiteral. got=%T", stmt.Expression)
+	}
+	if literal.Value != 5 {
+		t.Errorf("literal.Value not %d. got=%d", 5, literal.Value)
+	}
+	if literal.TokenLiteral() != "5" {
+		t.Errorf("literal.TokenLiteral not %s. got=%s", "5",
+			literal.TokenLiteral())
+	}
+}
+
+func TestParsingPrefixExpressions(t *testing.T) {
+	prefixTests := []struct {
+		input    string
+		operator string
+		value    interface{}
+	}{
+		{"!5;", "!", 5},
+		{"-15;", "-", 15},
+		{"!foobar;", "!", "foobar"},
+		{"-foobar;", "-", "foobar"},
+		{"!true;", "!", true},
+		{"!false;", "!", false},
+	}
+
+	for _, tt := range prefixTests {
+		l := lexer.New(tt.input)
+		p := New(l)
+		program := p.ParseProgram()
+		checkParserErrors(t, p)
+
+		if len(program.Statements) != 1 {
+			t.Fatalf("program.Statements does not contain %d statements. got=%d\n",
+				1, len(program.Statements))
+		}
+
+		stmt, ok := program.Statements[0].(*ast.ExpressionStatement)
+		if !ok {
+			t.Fatalf("program.Statements[0] is not ast.ExpressionStatement. got=%T",
+				program.Statements[0])
+		}
+
+		exp, ok := stmt.Expression.(*ast.PrefixExpression)
+		if !ok {
+			t.Fatalf("stmt is not ast.PrefixExpression. got=%T", stmt.Expression)
+		}
+		if exp.Operator != tt.operator {
+			t.Fatalf("exp.Operator is not '%s'. got=%s",
+				tt.operator, exp.Operator)
+		}
+		if !testLiteralExpression(t, exp.Right, tt.value) {
+			return
+		}
+	}
+}
+
+func TestParsingInfixExpressions(t *testing.T) {
+	infixTests := []struct {
+		input      string
+		leftValue  interface{}
+		operator   string
+		rightValue interface{}
+	}{
+		{"5 + 5;", 5, "+", 5},
+		{"5 - 5;", 5, "-", 5},
+		{"5 * 5;", 5, "*", 5},
+		{"5 / 5;", 5, "/", 5},
+		{"5 > 5;", 5, ">", 5},
+		{"5 < 5;", 5, "<", 5},
+		{"5 == 5;", 5, "==", 5},
+		{"5 != 5;", 5, "!=", 5},
+		{"foobar + barfoo;", "foobar", "+", "barfoo"},
+		{"foobar - barfoo;", "foobar", "-", "barfoo"},
+		{"foobar * barfoo;", "foobar", "*", "barfoo"},
+		{"foobar / barfoo;", "foobar", "/", "barfoo"},
+		{"foobar > barfoo;", "foobar", ">", "barfoo"},
+		{"foobar < barfoo;", "foobar", "<", "barfoo"},
+		{"foobar == barfoo;", "foobar", "==", "barfoo"},
+		{"foobar != barfoo;", "foobar", "!=", "barfoo"},
+		{"true == true", true, "==", true},
+		{"true != false", true, "!=", false},
+		{"false == false", false, "==", false},
+	}
+
+	for _, tt := range infixTests {
+		l := lexer.New(tt.input)
+		p := New(l)
+		program := p.ParseProgram()
+		checkParserErrors(t, p)
+
+		if len(program.Statements) != 1 {
+			t.Fatalf("program.Statements does not contain %d statements. got=%d\n",
+				1, len(program.Statements))
+		}
+
+		stmt, ok := program.Statements[0].(*ast.ExpressionStatement)
+		if !ok {
+			t.Fatalf("program.Statements[0] is not ast.ExpressionStatement. got=%T",
+				program.Statements[0])
+		}
+
+		if !testInfixExpression(t, stmt.Expression, tt.leftValue,
+			tt.operator, tt.rightValue) {
+			return
+		}
+	}
+}
+
+func TestOperatorPrecedenceParsing(t *testing.T) {
+	tests := []struct {
+		input    string
+		expected string
+	}{
+		{
+			"-a * b",
+			"((-a) * b)",
+		},
+		{
+			"!-a",
+			"(!(-a))",
+		},
+		{
+			"a + b + c",
+			"((a + b) + c)",
+		},
+		{
+			"a + b - c",
+			"((a + b) - c)",
+		},
+		{
+			"a * b * c",
+			"((a * b) * c)",
+		},
+		{
+			"a * b / c",
+			"((a * b) / c)",
+		},
+		{
+			"a + b / c",
+			"(a + (b / c))",
+		},
+		{
+			"a + b * c + d / e - f",
+			"(((a + (b * c)) + (d / e)) - f)",
+		},
+		{
+			"3 + 4; -5 * 5",
+			"(3 + 4)((-5) * 5)",
+		},
+		{
+			"5 > 4 == 3 < 4",
+			"((5 > 4) == (3 < 4))",
+		},
+		{
+			"5 < 4 != 3 > 4",
+			"((5 < 4) != (3 > 4))",
+		},
+		{
+			"3 + 4 * 5 == 3 * 1 + 4 * 5",
+			"((3 + (4 * 5)) == ((3 * 1) + (4 * 5)))",
+		},
+		{
+			"true",
+			"true",
+		},
+		{
+			"false",
+			"false",
+		},
+		{
+			"3 > 5 == false",
+			"((3 > 5) == false)",
+		},
+		{
+			"3 < 5 == true",
+			"((3 < 5) == true)",
+		},
+		{
+			"1 + (2 + 3) + 4",
+			"((1 + (2 + 3)) + 4)",
+		},
+		{
+			"(5 + 5) * 2",
+			"((5 + 5) * 2)",
+		},
+		{
+			"2 / (5 + 5)",
+			"(2 / (5 + 5))",
+		},
+		{
+			"(5 + 5) * 2 * (5 + 5)",
+			"(((5 + 5) * 2) * (5 + 5))",
+		},
+		{
+			"-(5 + 5)",
+			"(-(5 + 5))",
+		},
+		{
+			"!(true == true)",
+			"(!(true == true))",
+		},
+		{
+			"a + add(b * c) + d",
+			"((a + add((b * c))) + d)",
+		},
+		{
+			"add(a, b, 1, 2 * 3, 4 + 5, add(6, 7 * 8))",
+			"add(a, b, 1, (2 * 3), (4 + 5), add(6, (7 * 8)))",
+		},
+		{
+			"add(a + b + c * d / f + g)",
+			"add((((a + b) + ((c * d) / f)) + g))",
+		},
+	}
+
+	for _, tt := range tests {
+		l := lexer.New(tt.input)
+		p := New(l)
+		program := p.ParseProgram()
+		checkParserErrors(t, p)
+
+		actual := program.String()
+		if actual != tt.expected {
+			t.Errorf("expected=%q, got=%q", tt.expected, actual)
+		}
+	}
+}
+
+func TestBooleanExpression(t *testing.T) {
+	tests := []struct {
+		input           string
+		expectedBoolean bool
+	}{
+		{"true;", true},
+		{"false;", false},
+	}
+
+	for _, tt := range tests {
+		l := lexer.New(tt.input)
+		p := New(l)
+		program := p.ParseProgram()
+		checkParserErrors(t, p)
+
+		if len(program.Statements) != 1 {
+			t.Fatalf("program has not enough statements. got=%d",
+				len(program.Statements))
+		}
+
+		stmt, ok := program.Statements[0].(*ast.ExpressionStatement)
+		if !ok {
+			t.Fatalf("program.Statements[0] is not ast.ExpressionStatement. got=%T",
+				program.Statements[0])
+		}
+
+		boolean, ok := stmt.Expression.(*ast.Boolean)
+		if !ok {
+			t.Fatalf("exp not *ast.Boolean. got=%T", stmt.Expression)
+		}
+		if boolean.Value != tt.expectedBoolean {
+			t.Errorf("boolean.Value not %t. got=%t", tt.expectedBoolean,
+				boolean.Value)
+		}
+	}
+}
+
+func TestIfExpression(t *testing.T) {
+	input := `if (x < y) { x }`
+
+	l := lexer.New(input)
+	p := New(l)
+	program := p.ParseProgram()
+	checkParserErrors(t, p)
+
+	if len(program.Statements) != 1 {
+		t.Fatalf("program.Body does not contain %d statements. got=%d\n",
+			1, len(program.Statements))
+	}
+
+	stmt, ok := program.Statements[0].(*ast.ExpressionStatement)
+	if !ok {
+		t.Fatalf("program.Statements[0] is not ast.ExpressionStatement. got=%T",
+			program.Statements[0])
+	}
+
+	exp, ok := stmt.Expression.(*ast.IfExpression)
+	if !ok {
+		t.Fatalf("stmt.Expression is not ast.IfExpression. got=%T",
+			stmt.Expression)
+	}
+
+	if !testInfixExpression(t, exp.Condition, "x", "<", "y") {
+		return
+	}
+
+	if len(exp.Consequence.Statements) != 1 {
+		t.Errorf("consequence is not 1 statements. got=%d\n",
+			len(exp.Consequence.Statements))
+	}
+
+	consequence, ok := exp.Consequence.Statements[0].(*ast.ExpressionStatement)
+	if !ok {
+		t.Fatalf("Statements[0] is not ast.ExpressionStatement. got=%T",
+			exp.Consequence.Statements[0])
+	}
+
+	if !testIdentifier(t, consequence.Expression, "x") {
+		return
+	}
+
+	if exp.Alternative != nil {
+		t.Errorf("exp.Alternative.Statements was not nil. got=%+v", exp.Alternative)
+	}
+}
+
+func TestIfElseExpression(t *testing.T) {
+	input := `if (x < y) { x } else { y }`
+
+	l := lexer.New(input)
+	p := New(l)
+	program := p.ParseProgram()
+	checkParserErrors(t, p)
+
+	if len(program.Statements) != 1 {
+		t.Fatalf("program.Body does not contain %d statements. got=%d\n",
+			1, len(program.Statements))
+	}
+
+	stmt, ok := program.Statements[0].(*ast.ExpressionStatement)
+	if !ok {
+		t.Fatalf("program.Statements[0] is not ast.ExpressionStatement. got=%T",
+			program.Statements[0])
+	}
+
+	exp, ok := stmt.Expression.(*ast.IfExpression)
+	if !ok {
+		t.Fatalf("stmt.Expression is not ast.IfExpression. got=%T", stmt.Expression)
+	}
+
+	if !testInfixExpression(t, exp.Condition, "x", "<", "y") {
+		return
+	}
+
+	if len(exp.Consequence.Statements) != 1 {
+		t.Errorf("consequence is not 1 statements. got=%d\n",
+			len(exp.Consequence.Statements))
+	}
+
+	consequence, ok := exp.Consequence.Statements[0].(*ast.ExpressionStatement)
+	if !ok {
+		t.Fatalf("Statements[0] is not ast.ExpressionStatement. got=%T",
+			exp.Consequence.Statements[0])
+	}
+
+	if !testIdentifier(t, consequence.Expression, "x") {
+		return
+	}
+
+	if len(exp.Alternative.Statements) != 1 {
+		t.Errorf("exp.Alternative.Statements does not contain 1 statements. got=%d\n",
+			len(exp.Alternative.Statements))
+	}
+
+	alternative, ok := exp.Alternative.Statements[0].(*ast.ExpressionStatement)
+	if !ok {
+		t.Fatalf("Statements[0] is not ast.ExpressionStatement. got=%T",
+			exp.Alternative.Statements[0])
+	}
+
+	if !testIdentifier(t, alternative.Expression, "y") {
+		return
+	}
+}
+
+func TestFunctionLiteralParsing(t *testing.T) {
+	input := `fn(x, y) { x + y; }`
+
+	l := lexer.New(input)
+	p := New(l)
+	program := p.ParseProgram()
+	checkParserErrors(t, p)
+
+	if len(program.Statements) != 1 {
+		t.Fatalf("program.Body does not contain %d statements. got=%d\n",
+			1, len(program.Statements))
+	}
+
+	stmt, ok := program.Statements[0].(*ast.ExpressionStatement)
+	if !ok {
+		t.Fatalf("program.Statements[0] is not ast.ExpressionStatement. got=%T",
+			program.Statements[0])
+	}
+
+	function, ok := stmt.Expression.(*ast.FunctionLiteral)
+	if !ok {
+		t.Fatalf("stmt.Expression is not ast.FunctionLiteral. got=%T",
+			stmt.Expression)
+	}
+
+	if len(function.Parameters) != 2 {
+		t.Fatalf("function literal parameters wrong. want 2, got=%d\n",
+			len(function.Parameters))
+	}
+
+	testLiteralExpression(t, function.Parameters[0], "x")
+	testLiteralExpression(t, function.Parameters[1], "y")
+
+	if len(function.Body.Statements) != 1 {
+		t.Fatalf("function.Body.Statements has not 1 statements. got=%d\n",
+			len(function.Body.Statements))
+	}
+
+	bodyStmt, ok := function.Body.Statements[0].(*ast.ExpressionStatement)
+	if !ok {
+		t.Fatalf("function body stmt is not ast.ExpressionStatement. got=%T",
+			function.Body.Statements[0])
+	}
+
+	testInfixExpression(t, bodyStmt.Expression, "x", "+", "y")
+}
+
+func TestFunctionParameterParsing(t *testing.T) {
+	tests := []struct {
+		input          string
+		expectedParams []string
+	}{
+		{input: "fn() {};", expectedParams: []string{}},
+		{input: "fn(x) {};", expectedParams: []string{"x"}},
+		{input: "fn(x, y, z) {};", expectedParams: []string{"x", "y", "z"}},
+	}
+
+	for _, tt := range tests {
+		l := lexer.New(tt.input)
+		p := New(l)
+		program := p.ParseProgram()
+		checkParserErrors(t, p)
+
+		stmt := program.Statements[0].(*ast.ExpressionStatement)
+		function := stmt.Expression.(*ast.FunctionLiteral)
+
+		if len(function.Parameters) != len(tt.expectedParams) {
+			t.Errorf("length parameters wrong. want %d, got=%d\n",
+				len(tt.expectedParams), len(function.Parameters))
+		}
+
+		for i, ident := range tt.expectedParams {
+			testLiteralExpression(t, function.Parameters[i], ident)
+		}
+	}
+}
+
+func TestCallExpressionParsing(t *testing.T) {
+	input := "add(1, 2 * 3, 4 + 5);"
+
+	l := lexer.New(input)
+	p := New(l)
+	program := p.ParseProgram()
+	checkParserErrors(t, p)
+
+	if len(program.Statements) != 1 {
+		t.Fatalf("program.Statements does not contain %d statements. got=%d\n",
+			1, len(program.Statements))
+	}
+
+	stmt, ok := program.Statements[0].(*ast.ExpressionStatement)
+	if !ok {
+		t.Fatalf("stmt is not ast.ExpressionStatement. got=%T",
+			program.Statements[0])
+	}
+
+	exp, ok := stmt.Expression.(*ast.CallExpression)
+	if !ok {
+		t.Fatalf("stmt.Expression is not ast.CallExpression. got=%T",
+			stmt.Expression)
+	}
+
+	if !testIdentifier(t, exp.Function, "add") {
+		return
+	}
+
+	if len(exp.Arguments) != 3 {
+		t.Fatalf("wrong length of arguments. got=%d", len(exp.Arguments))
+	}
+
+	testLiteralExpression(t, exp.Arguments[0], 1)
+	testInfixExpression(t, exp.Arguments[1], 2, "*", 3)
+	testInfixExpression(t, exp.Arguments[2], 4, "+", 5)
+}
+
+func TestCallExpressionParameterParsing(t *testing.T) {
+	tests := []struct {
+		input         string
+		expectedIdent string
+		expectedArgs  []string
+	}{
+		{
+			input:         "add();",
+			expectedIdent: "add",
+			expectedArgs:  []string{},
+		},
+		{
+			input:         "add(1);",
+			expectedIdent: "add",
+			expectedArgs:  []string{"1"},
+		},
+		{
+			input:         "add(1, 2 * 3, 4 + 5);",
+			expectedIdent: "add",
+			expectedArgs:  []string{"1", "(2 * 3)", "(4 + 5)"},
+		},
+	}
+
+	for _, tt := range tests {
+		l := lexer.New(tt.input)
+		p := New(l)
+		program := p.ParseProgram()
+		checkParserErrors(t, p)
+
+		stmt := program.Statements[0].(*ast.ExpressionStatement)
+		exp, ok := stmt.Expression.(*ast.CallExpression)
+		if !ok {
+			t.Fatalf("stmt.Expression is not ast.CallExpression. got=%T",
+				stmt.Expression)
+		}
+
+		if !testIdentifier(t, exp.Function, tt.expectedIdent) {
+			return
+		}
+
+		if len(exp.Arguments) != len(tt.expectedArgs) {
+			t.Fatalf("wrong number of arguments. want=%d, got=%d",
+				len(tt.expectedArgs), len(exp.Arguments))
+		}
+
+		for i, arg := range tt.expectedArgs {
+			if exp.Arguments[i].String() != arg {
+				t.Errorf("argument %d wrong. want=%q, got=%q", i,
+					arg, exp.Arguments[i].String())
+			}
+		}
+	}
+}
+
+func testLetStatement(t *testing.T, s ast.Statement, name string) bool {
+	if s.TokenLiteral() != "let" {
+		t.Errorf("s.TokenLiteral not 'let'. got=%q", s.TokenLiteral())
+		return false
+	}
+
+	letStmt, ok := s.(*ast.LetStatement)
+	if !ok {
+		t.Errorf("s not *ast.LetStatement. got=%T", s)
+		return false
+	}
+
+	if letStmt.Name.Value != name {
+		t.Errorf("letStmt.Name.Value not '%s'. got=%s", name, letStmt.Name.Value)
+		return false
+	}
+
+	if letStmt.Name.TokenLiteral() != name {
+		t.Errorf("s.Name not '%s'. got=%s", name, letStmt.Name)
+		return false
+	}
+
+	return true
+}
+
+func testInfixExpression(t *testing.T, exp ast.Expression, left interface{},
+	operator string, right interface{}) bool {
+
+	opExp, ok := exp.(*ast.InfixExpression)
+	if !ok {
+		t.Errorf("exp is not ast.OperatorExpression. got=%T(%s)", exp, exp)
+		return false
+	}
+
+	if !testLiteralExpression(t, opExp.Left, left) {
+		return false
+	}
+
+	if opExp.Operator != operator {
+		t.Errorf("exp.Operator is not '%s'. got=%q", operator, opExp.Operator)
+		return false
+	}
+
+	if !testLiteralExpression(t, opExp.Right, right) {
+		return false
+	}
+
+	return true
+}
+
+func testLiteralExpression(
+	t *testing.T,
+	exp ast.Expression,
+	expected interface{},
+) bool {
+	switch v := expected.(type) {
+	case int:
+		return testIntegerLiteral(t, exp, int64(v))
+	case int64:
+		return testIntegerLiteral(t, exp, v)
+	case string:
+		return testIdentifier(t, exp, v)
+	case bool:
+		return testBooleanLiteral(t, exp, v)
+	}
+	t.Errorf("type of exp not handled. got=%T", exp)
+	return false
+}
+
+func testIntegerLiteral(t *testing.T, il ast.Expression, value int64) bool {
+	integ, ok := il.(*ast.IntegerLiteral)
+	if !ok {
+		t.Errorf("il not *ast.IntegerLiteral. got=%T", il)
+		return false
+	}
+
+	if integ.Value != value {
+		t.Errorf("integ.Value not %d. got=%d", value, integ.Value)
+		return false
+	}
+
+	if integ.TokenLiteral() != fmt.Sprintf("%d", value) {
+		t.Errorf("integ.TokenLiteral not %d. got=%s", value,
+			integ.TokenLiteral())
+		return false
+	}
+
+	return true
+}
+
+func testIdentifier(t *testing.T, exp ast.Expression, value string) bool {
+	ident, ok := exp.(*ast.Identifier)
+	if !ok {
+		t.Errorf("exp not *ast.Identifier. got=%T", exp)
+		return false
+	}
+
+	if ident.Value != value {
+		t.Errorf("ident.Value not %s. got=%s", value, ident.Value)
+		return false
+	}
+
+	if ident.TokenLiteral() != value {
+		t.Errorf("ident.TokenLiteral not %s. got=%s", value,
+			ident.TokenLiteral())
+		return false
+	}
+
+	return true
+}
+
+func testBooleanLiteral(t *testing.T, exp ast.Expression, value bool) bool {
+	bo, ok := exp.(*ast.Boolean)
+	if !ok {
+		t.Errorf("exp not *ast.Boolean. got=%T", exp)
+		return false
+	}
+
+	if bo.Value != value {
+		t.Errorf("bo.Value not %t. got=%t", value, bo.Value)
+		return false
+	}
+
+	if bo.TokenLiteral() != fmt.Sprintf("%t", value) {
+		t.Errorf("bo.TokenLiteral not %t. got=%s",
+			value, bo.TokenLiteral())
+		return false
+	}
+
+	return true
+}
+
+func checkParserErrors(t *testing.T, p *Parser) {
+	errors := p.Errors()
+	if len(errors) == 0 {
+		return
+	}
+
+	t.Errorf("parser has %d errors", len(errors))
+	for _, msg := range errors {
+		t.Errorf("parser error: %q", msg)
+	}
+	t.FailNow()
+}

monkey2/parser/parser_tracing.go

@@ -0,0 +1,32 @@
+package parser
+
+import (
+	"fmt"
+	"strings"
+)
+
+var traceLevel int = 0
+
+const traceIdentPlaceholder string = "\t"
+
+func identLevel() string {
+	return strings.Repeat(traceIdentPlaceholder, traceLevel-1)
+}
+
+func tracePrint(fs string) {
+	fmt.Printf("%s%s\n", identLevel(), fs)
+}
+
+func incIdent() { traceLevel = traceLevel + 1 }
+func decIdent() { traceLevel = traceLevel - 1 }
+
+func trace(msg string) string {
+	incIdent()
+	tracePrint("BEGIN " + msg)
+	return msg
+}
+
+func untrace(msg string) {
+	tracePrint("END " + msg)
+	decIdent()
+}

monkey2/repl/repl.go

@@ -0,0 +1,59 @@
+package repl
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+
+	"gitea.paas.celticinfo.fr/oabrivard/monkeylang/monkey2/lexer"
+	"gitea.paas.celticinfo.fr/oabrivard/monkeylang/monkey2/parser"
+)
+
+const PROMPT = ">> "
+
+func Start(in io.Reader, out io.Writer) {
+	scanner := bufio.NewScanner(in)
+
+	for {
+		fmt.Printf(PROMPT)
+		scanned := scanner.Scan()
+		if !scanned {
+			return
+		}
+
+		line := scanner.Text()
+		l := lexer.New(line)
+		p := parser.New(l)
+
+		program := p.ParseProgram()
+		if len(p.Errors()) != 0 {
+			printParserErrors(out, p.Errors())
+			continue
+		}
+
+		io.WriteString(out, program.String())
+		io.WriteString(out, "\n")
+	}
+}
+
+const MONKEY_FACE = `            __,__
+   .--.  .-"     "-.  .--.
+  / .. \/  .-. .-.  \/ .. \
+ | |  '|  /   Y   \  |'  | |
+ | \   \  \ 0 | 0 /  /   / |
+  \ '- ,\.-"""""""-./, -' /
+   ''-' /_   ^ ^   _\ '-''
+       |  \._   _./  |
+       \   \ '~' /   /
+        '._ '-=-' _.'
+           '-----'
+`
+
+func printParserErrors(out io.Writer, errors []string) {
+	io.WriteString(out, MONKEY_FACE)
+	io.WriteString(out, "Woops! We ran into some monkey business here!\n")
+	io.WriteString(out, " parser errors:\n")
+	for _, msg := range errors {
+		io.WriteString(out, "\t"+msg+"\n")
+	}
+}

monkey2/token/token.go

@@ -0,0 +1,66 @@
+package token
+
+type TokenType string
+
+const (
+	ILLEGAL = "ILLEGAL"
+	EOF     = "EOF"
+
+	// Identifiers + literals
+	IDENT = "IDENT" // add, foobar, x, y, ...
+	INT   = "INT"   // 1343456
+
+	// Operators
+	ASSIGN   = "="
+	PLUS     = "+"
+	MINUS    = "-"
+	BANG     = "!"
+	ASTERISK = "*"
+	SLASH    = "/"
+
+	LT = "<"
+	GT = ">"
+
+	EQ     = "=="
+	NOT_EQ = "!="
+
+	// Delimiters
+	COMMA     = ","
+	SEMICOLON = ";"
+
+	LPAREN = "("
+	RPAREN = ")"
+	LBRACE = "{"
+	RBRACE = "}"
+
+	// Keywords
+	FUNCTION = "FUNCTION"
+	LET      = "LET"
+	TRUE     = "TRUE"
+	FALSE    = "FALSE"
+	IF       = "IF"
+	ELSE     = "ELSE"
+	RETURN   = "RETURN"
+)
+
+type Token struct {
+	Type    TokenType
+	Literal string
+}
+
+var keywords = map[string]TokenType{
+	"fn":     FUNCTION,
+	"let":    LET,
+	"true":   TRUE,
+	"false":  FALSE,
+	"if":     IF,
+	"else":   ELSE,
+	"return": RETURN,
+}
+
+func LookupIdent(ident string) TokenType {
+	if tok, ok := keywords[ident]; ok {
+		return tok
+	}
+	return IDENT
+}