§2.8 Boolean literals.

ast/ast.go

@@ -6,6 +6,7 @@ import (
 	"code.osinet.fr/fgm/waiig15/token"
 )
 
+// The base Node interface
 // Node is the interface implemented by every node in the AST. It extends the
 // fmt.Stringer interface, allowing simple printing of nodes.
 type Node interface {
@@ -14,6 +15,7 @@ type Node interface {
 	String() string
 }
 
+// All statement nodes implement this
 // Statement extends Node and is only a way to differentiate between expressions
 // and statements.
 type Statement interface {
@@ -21,6 +23,7 @@ type Statement interface {
 	statementNode()
 }
 
+// All expression nodes implement this
 // Expression extends Node and is only a way to differentiate between
 // expressions and statements.
 type Expression interface {
@@ -155,6 +158,20 @@ func (i *Identifier) String() string {
 	return i.Value
 }
 
+// Boolean is the Node type for booleans.
+type Boolean struct {
+	Token token.Token
+	Value bool // true or false, for the equivalent Monkey tokens.
+}
+
+func (b *Boolean) expressionNode() {}
+func (b *Boolean) TokenLiteral() string {
+	return b.Token.Literal
+}
+func (b *Boolean) String() string {
+	return b.Token.Literal
+}
+
 // IntegerLiteral fulfills ast.Expression.
 type IntegerLiteral struct {
 	Token token.Token

parser/parser.go

@@ -63,6 +63,8 @@ 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)
 	for _, tok := range []token.TokenType{
@@ -328,6 +330,15 @@ func (p *Parser) parseInfixExpression(left ast.Expression) ast.Expression {
 	return expression
 }
 
+func (p *Parser) parseBoolean() ast.Expression {
+	defer untrace(trace("parseBoolean"))
+	expression := &ast.Boolean{
+		Token: p.curToken,
+		Value: p.curTokenIs(token.TRUE),
+	}
+	return expression
+}
+
 func (p *Parser) registerPrefix(tokenType token.TokenType, fn prefixParseFn) {
 	p.prefixParseFns[tokenType] = fn
 }

parser/parser_test.go

@@ -150,12 +150,14 @@ 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 {
@@ -186,7 +188,8 @@ func TestParsingPrefixExpressions(t *testing.T) {
 				tt.operator, exp.Operator)
 		}
 
-		if !testIntegerLiteral(t, exp.Right, tt.integerValue) {
+		if !testLiteralExpression(t, exp.Right, tt.value) {
+			// No error message, they have already been generated in testLiteralExpression.
 			return
 		}
 	}
@@ -195,9 +198,9 @@ func TestParsingPrefixExpressions(t *testing.T) {
 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},
@@ -207,6 +210,9 @@ 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 {
@@ -231,18 +237,8 @@ func TestParsingInfixExpressions(t *testing.T) {
 			t.Fatalf("exp is not infixExpression. got=%T", stmt.Expression)
 		}
 
-		// Why no error ?
-		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)
-		}
-
-		// Why no error ?
-		if !testIntegerLiteral(t, exp.Right, tt.rightValue) {
+		if !testInfixExpression(t, exp, tt.leftValue, tt.operator, tt.rightValue) {
+			// No error message, they have already been generated in testInfixExpression.
 			return
 		}
 	}
@@ -301,6 +297,22 @@ 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 {
@@ -316,6 +328,43 @@ func TestOperatorPrecedenceParsing(t *testing.T) {
 	}
 }
 
+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 testLetStatement(t *testing.T, s ast.Statement, name string) bool {
 	if s.TokenLiteral() != "let" {
 		t.Errorf("s.TokenLiteral not 'let'. got=%q", s.TokenLiteral())
@@ -385,6 +434,8 @@ func testLiteralExpression(
 		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
@@ -432,6 +483,26 @@ func testIdentifier(t *testing.T, exp ast.Expression, value string) bool {
 	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 true
+}
+
 func checkParserErrors(t *testing.T, p *Parser) {
 	errors := p.Errors()
 	if len(errors) == 0 {