parser: finish let and return expressions

ast/ast.go

@@ -257,3 +257,29 @@ func (fl *FunctionLiteral) String() string {
 
 	return out.String()
 }
+
+type CallExpression struct {
+	Token     token.Token // the `(` 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()
+}

parser/parser.go

@@ -34,6 +34,7 @@ var precedences = map[token.TokenType]int{
 	token.MINUS:    SUM,
 	token.SLASH:    PRODUCT,
 	token.ASTERISK: PRODUCT,
+	token.LPAREN:   CALL,
 }
 
 type Parser struct {
@@ -76,6 +77,7 @@ 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)
 
 	return p
 }
@@ -137,8 +139,11 @@ func (p *Parser) parseLetStatement() *ast.LetStatement {
 		return nil
 	}
 
-	// TODO: We're skipping the expressions until we encounter a semicolon
-	for !p.curTokenIs(token.SEMICOLON) {
+	p.nextToken()
+
+	stmt.Value = p.parseExpression(LOWEST)
+
+	if p.peekTokenIs(token.SEMICOLON) {
 		p.nextToken()
 	}
 
@@ -150,8 +155,9 @@ func (p *Parser) parseReturnStatement() *ast.ReturnStatement {
 
 	p.nextToken()
 
-	// TODO: We're skipping the expressions until we encounter a semicolon
-	for !p.curTokenIs(token.SEMICOLON) {
+	stmt.ReturnValue = p.parseExpression(LOWEST)
+
+	if p.peekTokenIs(token.SEMICOLON) {
 		p.nextToken()
 	}
 
@@ -349,6 +355,37 @@ func (p *Parser) parseFunctionParameters() []*ast.Identifier {
 	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{}
+
+	p.nextToken()
+
+	if p.peekTokenIs(token.RPAREN) {
+		return args
+	}
+
+	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) expectPeek(t token.TokenType) bool {
 	if p.peekTokenIs(t) {
 		p.nextToken()

parser/parser_test.go

@@ -9,68 +9,62 @@ import (
 )
 
 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")
-	}
-
-	if len(program.Statements) != 3 {
-		t.Fatalf("program.Statements does not contain 3 statements. got=%d", len(program.Statements))
-	}
-
 	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 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) {
-	input := `
-return 5;
-return 10;
-return 993322;
-	`
-
-	l := lexer.New(input)
-	p := New(l)
-
-	program := p.ParseProgram()
-	checkParserErrors(t, p)
-
-	if len(program.Statements) != 3 {
-		t.Fatalf("program.Statements does not contain 3 statements. got=%d", len(program.Statements))
+	tests := []struct {
+		input         string
+		expectedValue interface{}
+	}{
+		{"return 5;", 5},
+		{"return true;", true},
+		{"return x;", "x"},
 	}
 
-	for _, stmt := range program.Statements {
-		returnStmt, ok := stmt.(*ast.ReturnStatement)
-		if !ok {
-			t.Errorf("stmt not *ast.ReturnStatement. got=%T", stmt)
-			continue
+	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))
 		}
 
-		if returnStmt.TokenLiteral() != "return" {
-			t.Errorf("returnStmt.TokenLiteral not 'return', got %q", returnStmt.TokenLiteral())
+		stmt := program.Statements[0]
+		val := stmt.(*ast.ReturnStatement).ReturnValue
+		if !testLiteralExpression(t, val, tt.expectedValue) {
+			return
 		}
 	}
 }
@@ -275,6 +269,18 @@ 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 {
@@ -489,6 +495,41 @@ func TestFunctionParametersParsing(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.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\n", 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. want 3, 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 testLetStatement(t *testing.T, s ast.Statement, name string) bool {
 	if s.TokenLiteral() != "let" {
 		t.Errorf("s.TokenLiteral not 'let'. got=%q", s.TokenLiteral())