37 parse call expressions

ast/ast.go

@@ -50,6 +50,30 @@ func (b *Boolean) expressionNode()      {}
 func (b *Boolean) TokenLiteral() string { return b.Token.Literal }
 func (b *Boolean) String() string       { return b.Token.Literal }
 
+type CallExpression struct {
+	Token     token.Token
+	Function  Expression
+	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 FunctionLiteral struct {
 	Token      token.Token
 	Parameters []*Identifier

parser/parser.go

@@ -30,6 +30,7 @@ var precedences = map[token.TokenType]int{
 	token.MINUS:    SUM,
 	token.SLASH:    PRODUCT,
 	token.ASTERISK: PRODUCT,
+	token.LPAREN:   CALL,
 }
 
 type Parser struct {
@@ -74,6 +75,7 @@ func New(l *lexer.Lexer) *Parser {
 	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 to set both curToken and peekToken
 	p.nextToken()
@@ -116,6 +118,36 @@ func (p *Parser) nextToken() {
 	p.peekToken = p.l.NextToken()
 }
 
+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) ParseProgram() *ast.Program {
 	program := &ast.Program{}
 	program.Statements = []ast.Statement{}
@@ -316,8 +348,12 @@ func (p *Parser) parseLetStatement() *ast.LetStatement {
 	if !p.expectPeek(token.ASSIGN) {
 		return nil
 	}
-	//	skip expression parsing for now
-	for !p.curTokenIs(token.SEMICOLON) {
+
+	p.nextToken()
+
+	stmt.Value = p.parseExpression(LOWEST)
+
+	for !p.curTokenIs(token.SEMICOLON) && !p.curTokenIs(token.EOF) {
 		p.nextToken()
 	}
 	return stmt
@@ -327,8 +363,10 @@ func (p *Parser) parseReturnStatement() *ast.ReturnStatement {
 	stmt := &ast.ReturnStatement{Token: p.curToken}
 
 	p.nextToken()
-	// skip expression parsing for now
-	for !p.curTokenIs(token.SEMICOLON) {
+
+	stmt.ReturnValue = p.parseExpression(LOWEST)
+
+	for !p.curTokenIs(token.SEMICOLON) && !p.curTokenIs(token.EOF) {
 		p.nextToken()
 	}
 

parser/parser_test.go

@@ -45,6 +45,41 @@ func TestBooleanExpression(t *testing.T) {
 	}
 }
 
+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 does not contain %d statements. got=%d", 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 number 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 TestIdentifierExpression(t *testing.T) {
 	input := "foobar;"
 
@@ -544,6 +579,18 @@ func TestOperatorPrecedenceParsing(t *testing.T) {
 			"!(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)
@@ -559,35 +606,38 @@ func TestOperatorPrecedenceParsing(t *testing.T) {
 }
 
 func TestLetStatements(t *testing.T) {
-	input := `
-let x = 5;
-let y = 10;
-let foobar = 838383;
-`
-
-	l := lexer.New(input)
-	p := New(l)
-
-	program := p.ParseProgram()
-	checkParserErrors(t, p)
-	if program == nil {
-		t.Fatalf("ParseProgram() returned nil")
-	}
-
 	tests := []struct {
+		input              string
 		expectedIdentifier string
+		expectedValue      interface{}
 	}{
-		{"x"},
-		{"y"},
-		{"foobar"},
+		{"let x = 5;", "x", 5},
+		{"let y = true;", "y", true},
+		{"let foobar = y;", "foobar", "y"},
 	}
 
-	for i, tt := range tests {
-		stmt := program.Statements[i]
+	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 statement. 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 testLetStatement(t *testing.T, s ast.Statement, name string) bool {