selectors support for hash

parser/parser.go

@@ -35,6 +35,7 @@ var precedences = map[token.TokenType]int{
 	token.ASTERISK: PRODUCT,
 	token.LPAREN:   CALL,
 	token.LBRACKET: INDEX,
+	token.DOT:      INDEX,
 }
 
 type (
@@ -89,6 +90,7 @@ func New(l *lexer.Lexer) *Parser {
 	p.registerInfix(token.LPAREN, p.parseCallExpression)
 	p.registerInfix(token.LBRACKET, p.parseIndexExpression)
 	p.registerInfix(token.ASSIGN, p.parseAssignmentExpression)
+	p.registerInfix(token.DOT, p.parseSelectorExpression)
 
 	// Read two tokens, so curToken and peekToken are both set
 	p.nextToken()
@@ -570,3 +572,9 @@ func (p *Parser) parseComment() ast.Statement {
 func (p *Parser) parseNull() ast.Expression {
 	return &ast.Null{Token: p.curToken}
 }
+
+func (p *Parser) parseSelectorExpression(expression ast.Expression) ast.Expression {
+	p.expectPeek(token.IDENT)
+	index := &ast.StringLiteral{Token: p.curToken, Value: p.curToken.Literal}
+	return &ast.IndexExpression{Left: expression, Index: index}
+}

parser/parser_test.go

@@ -358,6 +358,10 @@ func TestOperatorPrecedenceParsing(t *testing.T) {
 			"add(a * b[2], b[1], 2 * [1, 2][1])",
 			"add((a * (b[2])), (b[1]), (2 * ([1, 2][1])))",
 		},
+		{
+			"d.foo * d.bar",
+			"((d[foo]) * (d[bar]))",
+		},
 	}
 
 	for _, tt := range tests {
@@ -831,6 +835,40 @@ func TestParsingArrayLiterals(t *testing.T) {
 	testInfixExpression(t, array.Elements[2], 3, "+", 3)
 }
 
+func TestParsingSelectorExpressions(t *testing.T) {
+	input := "myHash.foo"
+
+	l := lexer.New(input)
+	p := New(l)
+	program := p.ParseProgram()
+	checkParserErrors(t, p)
+	stmt, ok := program.Statements[0].(*ast.ExpressionStatement)
+	t.Logf("stmt: %#v", stmt)
+
+	exp, ok := stmt.Expression.(*ast.IndexExpression)
+	if !ok {
+		t.Fatalf("exp not *ast.IndexExpression. got=%T", stmt.Expression)
+	}
+
+	ident, ok := exp.Left.(*ast.Identifier)
+	if !ok {
+		t.Fatalf("exp.Left not *ast.Identifier. got=%T", stmt.Expression)
+	}
+
+	if !testIdentifier(t, ident, "myHash") {
+		return
+	}
+
+	index, ok := exp.Index.(*ast.StringLiteral)
+	if !ok {
+		t.Fatalf("exp.Index not *ast.StringLiteral. got=%T", stmt.Expression)
+	}
+
+	if index.Value != "foo" {
+		t.Fatalf("index.Value != \"foo\"")
+	}
+}
+
 func TestParsingIndexExpressions(t *testing.T) {
 	input := "myArray[1 + 1]"