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| <H2>21.2 Fundamental Datatypes</H2> |
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| <P>The C++ Standard Library describes a specific type by providing a specialization of the<SAMP> numeric_limits</SAMP> template for the type. Static member functions and static constant data members then provide information specific to the type. The C++ Standard Library includes descriptions of the fundamental datatypes given in <A HREF="21-2.html#Table 21">Table 21</A>.</P> |
| <H4><A NAME="Table 21">Table 21: Fundamental datatypes of the C++ Standard Library </A></H4> |
| <TABLE BORDER="1" CELLPADDING="3" CELLSPACING="3"> |
| <tr><td valign=top><B><SAMP>bool</SAMP></B> |
| </td><td valign=top><B><SAMP>char</SAMP></B> |
| </td><td valign=top><B><SAMP>int</SAMP></B> |
| </td><td valign=top><B><SAMP>float</SAMP></B> |
| </td></tr> |
| <tr><td valign=top colspan=1 rowspan=6> |
| </td><td valign=top><P CLASS="TABLE"><SAMP>signed char</SAMP></P> |
| </td><td valign=top><P CLASS="TABLE"><SAMP>short</SAMP></P> |
| </td><td valign=top><P CLASS="TABLE"><SAMP>double</SAMP></P> |
| </td></tr> |
| <tr><td valign=top><P CLASS="TABLE"><SAMP>unsigned char</SAMP></P> |
| </td><td valign=top><P CLASS="TABLE"><SAMP>long</SAMP></P> |
| </td><td valign=top><P CLASS="TABLE"><SAMP>long double</SAMP></P> |
| </td></tr> |
| <tr><td valign=top colspan=1 rowspan=4> |
| </td><td valign=top><P CLASS="TABLE"><SAMP>wchar_t</SAMP></P> |
| </td><td valign=top colspan=1 rowspan=4> |
| </td></tr> |
| <tr><td valign=top><P CLASS="TABLE"><SAMP>unsigned short</SAMP></P> |
| </td></tr> |
| <tr><td valign=top><P CLASS="TABLE"><SAMP>unsigned int</SAMP></P> |
| </td></tr> |
| <tr><td valign=top><P CLASS="TABLE"><SAMP>unsigned long</SAMP></P> |
| </td></tr> |
| </TABLE> |
| <P>Certain implementations may also provide information on other datatypes. Whether or not an implementation is described can be discovered using the static data member <SAMP>is_specialized</SAMP>. For example, the following is legal, and will indicate that the <B><I><A HREF="../stdlibref/basic-string.html">string</A></I></B> datatype is not described by this mechanism.</P> |
| |
| <UL><PRE> |
| std::cout << "are strings described " << |
| std::numeric_limits<string>::is_specialized << std::endl; |
| </PRE></UL> |
| <P>For datatypes that do not have a specialization, the values yielded by the functions and data members in <SAMP>numeric_limits</SAMP> are generally zero or <SAMP>false</SAMP>.</P> |
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