1 <?xml version="1.0" encoding="utf-8"?>

     2 <!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. -->

     3 <!-- This component and the accompanying materials are made available under the terms of the License 

     4 "Eclipse Public License v1.0" which accompanies this distribution, 

     5 and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". -->

     6 <!-- Initial Contributors:

     7     Nokia Corporation - initial contribution.

     8 Contributors: 

     9 -->

    10 <!DOCTYPE concept

    11   PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">

    12 <concept id="GUID-189FBB0E-0A47-5CCC-9209-DC69E76DE6B3" xml:lang="en"><title>Boolean</title><shortdesc>This document describes the Boolean data types.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

    13 <p><xref href="GUID-4B942C06-1BAC-3A21-B3B1-89FB5C51ADA0.dita"><apiname>TBool</apiname></xref> represents a Boolean whose value may be <codeph>ETrue</codeph> or <codeph>EFalse</codeph>.

    14 It is implemented as a natural machine-word integer.</p>

    15 <p>The C language defines logical expressions to <i>produce</i> 0 for false,

    16 1 for true, and to <i>interpret</i> 0 as false, non-zero as true. This confusion

    17 cannot be altogether avoided with <codeph>TBool</codeph>. It is possible,

    18 but strongly deprecated, to assign numeric values to a <xref href="GUID-4B942C06-1BAC-3A21-B3B1-89FB5C51ADA0.dita"><apiname>TBool</apiname></xref>.</p>

    19 <p>In general, a <xref href="GUID-4B942C06-1BAC-3A21-B3B1-89FB5C51ADA0.dita"><apiname>TBool</apiname></xref> should be tested using</p>

    20 <codeblock id="GUID-BF6AF640-D03A-5335-B67B-3852C2808833" xml:space="preserve">if (x) ...</codeblock>

    21 <p>or</p>

    22 <codeblock id="GUID-D00FBCFD-57C2-5D1E-999A-0567AFBAA258" xml:space="preserve">if (!x) ...</codeblock>

    23 <p>rather than</p>

    24 <codeblock id="GUID-41D4B777-217D-5BA5-B44A-59C2419FB2D6" xml:space="preserve">if (x==ETrue) ...</codeblock>

    25 <p>or</p>

    26 <codeblock id="GUID-72F416BC-213F-5731-B26A-8ECE2916935B" xml:space="preserve">if (x==EFalse) ...</codeblock>

    27 <p>The <xref href="GUID-4B942C06-1BAC-3A21-B3B1-89FB5C51ADA0.dita"><apiname>TBool</apiname></xref> uses a whole machine word. When a class has

    28 a number of flags, they should be encoded in a flags byte, and suitable getter/setter

    29 functions, taking <xref href="GUID-4B942C06-1BAC-3A21-B3B1-89FB5C51ADA0.dita"><apiname>TBool</apiname></xref> s, should be coded to access that

    30 flags byte.</p>

    31 </conbody></concept>