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

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     7     Nokia Corporation - initial contribution.

     8 Contributors: 

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    10 <!DOCTYPE concept

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

    12 <concept id="GUID-6C1E4B3D-0FBF-5CEA-9A30-B4C5CB4CAC3E" xml:lang="en"><title>Coding

    13 literal descriptors</title><shortdesc>Literal descriptors must be defined in their own C++ statement

    14 and the resulting constant used wherever it is required.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

    15 <p> Literal descriptors cannot be embedded in expressions because they do

    16 not create temporary objects.</p>

    17 <p>Literal objects can be declared safely in header files:</p>

    18 <ul>

    19 <li id="GUID-1EEAF77A-63B1-5191-95D7-6F24FAC6B94C"><p>without requiring writable

    20 data</p> </li>

    21 <li id="GUID-BED08A91-2EAF-53CB-9B23-8F63D5658303"><p>without creating a copy

    22 of the data in every module that includes the header.</p> </li>

    23 </ul>

    24 <p>Literals can be defined at file-scope, including in header files, in which

    25 case they are visible to any code that follows. They can also be declared

    26 local to the function which uses them. However, there are a couple of caveats

    27 with defining them at function scope:</p>

    28 <ul>

    29 <li id="GUID-9193E180-8358-5BB9-8A76-5EAB4753FB4E"><p>For very short strings,

    30 of the order of 3 ASCII characters or 1 UNICODE character, it is more efficient

    31 to declare the literals at file scope.</p> </li>

    32 <li id="GUID-CAEF761B-7E05-58C7-968E-FF9C31413FFB"><p>Literal descriptors

    33 defined in inline functions are laid down in <i>every single</i> compilation

    34 module that includes the header file.</p> </li>

    35 </ul>

    36 <p>Thus, if the descriptor is short or used only in an inline function, it

    37 is better to define it at file scope with a suitably distinct name.</p>

    38 </conbody></concept>