2.8: Add boolean

ast/ast.go

@@ -150,3 +150,12 @@ func (ie *InfixExpression) String() string {
 
 	return out.String()
 }
+
+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 }

parser/parser.go

@@ -62,6 +62,8 @@ func New(l *lexer.Lexer) *Parser {
 	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.infixParseFns = make(map[token.TokenType]infixParseFn)
 	p.registerInfix(token.PLUS, p.parseInfixExpression)
@@ -280,3 +282,10 @@ func (p *Parser) parseInfixExpression(left ast.Expression) ast.Expression {
 
 	return expression
 }
+
+func (p *Parser) parseBoolean() ast.Expression {
+	return &ast.Boolean{
+		Token: p.curToken,
+		Value: p.curTokenIs(token.TRUE),
+	}
+}

parser/parser_test.go

@@ -166,12 +166,14 @@ func TestIntegerLiteralExpression(t *testing.T) {
 
 func TestParsingPrefixExpressions(t *testing.T) {
 	prefixTests := []struct {
-		input        string
-		operator     string
-		integerValue int64
+		input    string
+		operator string
+		value    interface{}
 	}{
 		{"!5;", "!", 5},
 		{"-15;", "-", 15},
+		{"!true;", "!", true},
+		{"!false;", "!", false},
 	}
 
 	for _, tt := range prefixTests {
@@ -199,7 +201,7 @@ func TestParsingPrefixExpressions(t *testing.T) {
 			t.Fatalf("exp.Operator is not '%s'. got=%s",
 				tt.operator, exp.Operator)
 		}
-		if !testIntegerLiteral(t, exp.Right, tt.integerValue) {
+		if !testLiteralExpression(t, exp.Right, tt.value) {
 			return
 		}
 	}
@@ -226,12 +228,77 @@ func testIntegerLiteral(t *testing.T, il ast.Expression, value int64) bool {
 	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 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 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.InfixExpression. 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 TestParsingInfixExpressions(t *testing.T) {
 	infixTests := []struct {
 		input      string
-		leftValue  int64
+		leftValue  interface{}
 		operator   string
-		rightValue int64
+		rightValue interface{}
 	}{
 		{"5 + 5;", 5, "+", 5},
 		{"5 - 5;", 5, "-", 5},
@@ -241,6 +308,9 @@ func TestParsingInfixExpressions(t *testing.T) {
 		{"5 < 5;", 5, "<", 5},
 		{"5 == 5;", 5, "==", 5},
 		{"5 != 5;", 5, "!=", 5},
+		{"true == true", true, "==", true},
+		{"true != false", true, "!=", false},
+		{"false == false", false, "==", false},
 	}
 
 	for _, tt := range infixTests {
@@ -265,16 +335,12 @@ func TestParsingInfixExpressions(t *testing.T) {
 			t.Fatalf("exp is not ast.InfixExpression. got=%T", stmt.Expression)
 		}
 
-		if !testIntegerLiteral(t, exp.Left, tt.leftValue) {
-			return
-		}
-
 		if exp.Operator != tt.operator {
 			t.Fatalf("exp.Operator is not '%s'. got=%s",
 				tt.operator, exp.Operator)
 		}
 
-		if !testIntegerLiteral(t, exp.Right, tt.rightValue) {
+		if !testInfixExpression(t, stmt.Expression, tt.leftValue, tt.operator, tt.rightValue) {
 			return
 		}
 	}
@@ -333,6 +399,22 @@ func TestOperatorPrecedenceParsing(t *testing.T) {
 			"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)",
+		},
 	}
 
 	for _, tt := range tests {
@@ -347,3 +429,52 @@ func TestOperatorPrecedenceParsing(t *testing.T) {
 		}
 	}
 }
+
+func TestBooleanExpression(t *testing.T) {
+	input := `true;`
+
+	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])
+	}
+
+	boolean, ok := stmt.Expression.(*ast.Boolean)
+	if !ok {
+		t.Fatalf("exp not *ast.Boolean. got=%T", stmt.Expression)
+	}
+	if boolean.Value != true {
+		t.Errorf("boolean.Value not %v. got=%v", true, boolean.Value)
+	}
+	if boolean.TokenLiteral() != "true" {
+		t.Errorf("boolean.TokenLiteral not %s. got=%s", "true", boolean.TokenLiteral())
+	}
+}
+
+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
+}