boolean and if/else

parser/parser_test.go

@@ -356,6 +356,114 @@ func TestOperatorPrecedenceParsing(t *testing.T) {
 	}
 }
 
+func TestIfExpression(t *testing.T) {
+	input := `if (x < y) { x }`
+
+	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",
+			program.Statements[0])
+	}
+
+	exp, ok := stmt.Expression.(*ast.IfExpression)
+	if !ok {
+		t.Fatalf("stmt.Expression is not ast.IfExpression. got=%T",
+			stmt.Expression)
+	}
+
+	if !testInfixExpression(t, exp.Condition, "x", "<", "y") {
+		return
+	}
+
+	if len(exp.Consequence.Statements) != 1 {
+		t.Errorf("consequence is not 1 statements. got=%d\n",
+			len(exp.Consequence.Statements))
+	}
+
+	consequence, ok := exp.Consequence.Statements[0].(*ast.ExpressionStatement)
+	if !ok {
+		t.Fatalf("Statements[0] is not ast.ExpressionStatement. got=%T",
+			exp.Consequence.Statements[0])
+	}
+
+	if !testIdentifier(t, consequence.Expression, "x") {
+		return
+	}
+
+	if exp.Alternative != nil {
+		t.Errorf("exp.Alternative.Statements was not nil. got=%+v", exp.Alternative)
+	}
+}
+
+func TestIfElseExpression(t *testing.T) {
+	input := `if (x < y) { x } else { y }`
+
+	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",
+			program.Statements[0])
+	}
+
+	exp, ok := stmt.Expression.(*ast.IfExpression)
+	if !ok {
+		t.Fatalf("stmt.Expression is not ast.IfExpression. got=%T", stmt.Expression)
+	}
+
+	if !testInfixExpression(t, exp.Condition, "x", "<", "y") {
+		return
+	}
+
+	if len(exp.Consequence.Statements) != 1 {
+		t.Errorf("consequence is not 1 statements. got=%d\n",
+			len(exp.Consequence.Statements))
+	}
+
+	consequence, ok := exp.Consequence.Statements[0].(*ast.ExpressionStatement)
+	if !ok {
+		t.Fatalf("Statements[0] is not ast.ExpressionStatement. got=%T",
+			exp.Consequence.Statements[0])
+	}
+
+	if !testIdentifier(t, consequence.Expression, "x") {
+		return
+	}
+
+	if len(exp.Alternative.Statements) != 1 {
+		t.Errorf("exp.Alternative.Statements does not contain 1 statements. got=%d\n",
+			len(exp.Alternative.Statements))
+	}
+
+	alternative, ok := exp.Alternative.Statements[0].(*ast.ExpressionStatement)
+	if !ok {
+		t.Fatalf("Statements[0] is not ast.ExpressionStatement. got=%T",
+			exp.Alternative.Statements[0])
+	}
+
+	if !testIdentifier(t, alternative.Expression, "y") {
+		return
+	}
+}
+
 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())
@@ -419,11 +527,34 @@ 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
 }
 
+func testBooleanLiteral(t *testing.T, exp ast.Expression, value bool) bool {
+	bo, ok := exp.(*ast.Boolean)
+	if !ok {
+		t.Errorf("exp *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("intboeg.TokenLiteral not %t. got=%s", value,
+			bo.TokenLiteral())
+		return false
+	}
+
+	return true
+}
+
 func testIntegerLiteral(t *testing.T, il ast.Expression, value int64) bool {
 	integ, ok := il.(*ast.IntegerLiteral)
 	if !ok {