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<HTML><HEAD><TITLE>21.3 Numeric Limit Members</TITLE></HEAD><BODY><A HREF="ug1.htm"><IMG SRC="images/banner.gif"></A><BR><A HREF="fun_3734.htm"><IMG SRC="images/prev.gif"></A><A HREF="booktoc1.htm"><IMG SRC="images/toc.gif"></A><A HREF="tindex1.htm"><IMG SRC="images/tindex.gif"></A><BR><STRONG>Click on the banner to return to the user guide home page.</STRONG><H2>21.3 Numeric Limit Members</H2><P>Since a number of the fields in the <SAMP>numeric_limits</SAMP> structure are meaningful only for floating point values, it is useful to separate the description of the members into common fields and floating-point specific fields.</P><A NAME="21.3.1"><H3>21.3.1 Members Common to All Types</H3></A><P>The following table summarizes the information available through the <A HREF="../stdlibcr/num_5679.htm"><B><I>numeric_limits</I></B></A> static member data fields and functions.</P><CENTER><TABLE BORDER CELLSPACING=3 CELLPADDING=3><TR VALIGN=top><TD>Type<BR></TD><TD>Name<BR></TD><TD>Meaning <BR></TD></TR><TR VALIGN=top><TD><SAMP>bool</SAMP><BR></TD><TD><SAMP>is_specialized</SAMP><BR></TD><TD>true if a specialization exists, false otherwise <BR></TD></TR><TR VALIGN=top><TD><SAMP>T</SAMP><BR></TD><TD><SAMP>min()</SAMP><BR></TD><TD>smallest finite value<BR></TD></TR><TR VALIGN=top><TD><SAMP>T</SAMP><BR></TD><TD><SAMP>max()</SAMP><BR></TD><TD>largest finite value<BR></TD></TR><TR VALIGN=top><TD><SAMP>int</SAMP><BR></TD><TD><SAMP>radix</SAMP><BR></TD><TD>the base of the representation<BR></TD></TR><TR VALIGN=top><TD><SAMP>int</SAMP><BR></TD><TD><SAMP>digits</SAMP><BR></TD><TD>number of <SAMP>radix</SAMP> digits that can be represented without change<BR></TD></TR><TR VALIGN=top><TD><SAMP>int</SAMP><BR></TD><TD><SAMP>digits10</SAMP><BR></TD><TD>number of base-10 digits that can be represented without change<BR></TD></TR><TR VALIGN=top><TD><SAMP>bool</SAMP><BR></TD><TD><SAMP>is_signed</SAMP><BR></TD><TD>true if the type is signed<BR></TD></TR><TR VALIGN=top><TD><SAMP>bool</SAMP><BR></TD><TD><SAMP>is_integer</SAMP><BR></TD><TD>true if the type is integer<BR></TD></TR><TR VALIGN=top><TD><SAMP>bool</SAMP><BR></TD><TD><SAMP>is_exact</SAMP><BR></TD><TD>true if the representation is exact<BR></TD></TR><TR VALIGN=top><TD><SAMP>bool</SAMP><BR></TD><TD><SAMP>is_bounded</SAMP><BR></TD><TD>true if representation is finite<BR></TD></TR><TR VALIGN=top><TD><SAMP>bool</SAMP><BR></TD><TD><SAMP>is_modulo</SAMP><BR></TD><TD>true if type is modulo<BR></TD></TR><TR VALIGN=top><TD><SAMP>bool</SAMP><BR></TD><TD><SAMP>traps</SAMP><BR></TD><TD>true if trapping is implemented for the type<BR></TD></TR></TABLE></CENTER><P>Radix represents the internal base for the representation. For example, most machines use a base 2 radix for integer data values, however some may also support a representation, such as BCD, that uses a different base. The <SAMP>digits</SAMP> field then represents the number of such radix values that can be held in a value. For an integer type, this would be the number of non-sign bits in the representation.</P><P>All fundamental types are bounded. However, an implementation might choose to include, for example, an infinite precision integer package that would not be bounded.</P><P>A type is <I>modulo</I> if the value resulting from the addition of two values can wrap around, that is, be smaller than either argument. The fundamental unsigned integer types are all modulo.</P><A NAME="21.3.2"><H3>21.3.2 Members Specific to Floating Point Values</H3></A><P>The following members are either specific to floating point values, or have a meaning slightly different for floating point values than the one described earlier for non-floating data types.</P><CENTER><TABLE BORDER CELLSPACING=3 CELLPADDING=3><TR VALIGN=top><TD>Type<BR></TD><TD>Name<BR></TD><TD>Meaning<BR></TD></TR><TR VALIGN=top><TD><SAMP>T</SAMP><BR></TD><TD><SAMP>min()</SAMP><BR></TD><TD>the minimum positive normalized value<BR></TD></TR><TR VALIGN=top><TD><SAMP>int</SAMP><BR></TD><TD><SAMP>digits</SAMP><BR></TD><TD>the number of digits in the mantissa<BR></TD></TR><TR VALIGN=top><TD><SAMP>int</SAMP><BR></TD><TD><SAMP>radix</SAMP><BR></TD><TD>the base (or radix) of the exponent representation<BR></TD></TR><TR VALIGN=top><TD><SAMP>T</SAMP><BR></TD><TD><SAMP>epsilon()</SAMP><BR></TD><TD>the difference between 1 and the least representable value greater than 1<BR></TD></TR><TR VALIGN=top><TD><SAMP>T</SAMP><BR></TD><TD><SAMP>round_error()</SAMP><BR></TD><TD>a measurement of the rounding error<BR></TD></TR><TR VALIGN=top><TD><SAMP>int</SAMP><BR></TD><TD><SAMP>min_exponent</SAMP><BR></TD><TD>minimum negative exponent<BR></TD></TR><TR VALIGN=top><TD><SAMP>int</SAMP><BR></TD><TD><SAMP>min_exponent10</SAMP><BR></TD><TD>minimum value such that 10 raised to that power is in range<BR></TD></TR><TR VALIGN=top><TD><SAMP>int</SAMP><BR></TD><TD><SAMP>max_exponent</SAMP><BR></TD><TD>maximum positive exponent<BR></TD></TR><TR VALIGN=top><TD><SAMP>int</SAMP><BR></TD><TD><SAMP>max_exponent10</SAMP><BR></TD><TD>maximum value such that 10 raised to that power is in range<BR></TD></TR><TR VALIGN=top><TD><SAMP>bool</SAMP><BR></TD><TD><SAMP>has_infinity</SAMP><BR></TD><TD>true if the type has a representation of positive infinity<BR></TD></TR><TR VALIGN=top><TD><SAMP>T</SAMP><BR></TD><TD><SAMP>infinity()</SAMP><BR></TD><TD>representation of infinity, if available<BR></TD></TR><TR VALIGN=top><TD><SAMP>bool</SAMP><BR></TD><TD><SAMP>has_quiet_NaN</SAMP><BR></TD><TD>true if there is a representation of a quiet ``Not a Number"<BR></TD></TR><TR VALIGN=top><TD><SAMP>T</SAMP><BR></TD><TD><SAMP>quiet_NaN()</SAMP><BR></TD><TD>representation of quiet NaN, if available<BR></TD></TR><TR VALIGN=top><TD><SAMP>bool</SAMP><BR></TD><TD><SAMP>has_signaling_NaN</SAMP><BR></TD><TD>true if there is a representation for a signaling NaN<BR></TD></TR><TR VALIGN=top><TD><SAMP>T</SAMP><BR></TD><TD><SAMP>signaling_NaN()</SAMP><BR></TD><TD>representation of signaling NaN, if available<BR></TD></TR><TR VALIGN=top><TD><SAMP>bool</SAMP><BR></TD><TD><SAMP>has_denorm</SAMP><BR></TD><TD>true if the representation allows denormalized values<BR></TD></TR><TR VALIGN=top><TD><SAMP>T</SAMP><BR></TD><TD><SAMP>denorm_min()</SAMP><BR></TD><TD>Minimum positive denormalized value <BR></TD></TR><TR VALIGN=top><TD><SAMP>bool</SAMP><BR></TD><TD><SAMP>is_iec559</SAMP><BR></TD><TD>true if representation adheres to IEC 559 standard.<BR></TD></TR><TR VALIGN=top><TD><SAMP>bool</SAMP><BR></TD><TD><SAMP>tinyness_before</SAMP><BR></TD><TD>true if <SAMP>tinyness</SAMP> is detected before rounding<BR></TD></TR><TR VALIGN=top><TD> </TD><TD><SAMP>round_style</SAMP><BR></TD><TD>rounding style for type<BR></TD></TR></TABLE></CENTER><P>For the <SAMP>float </SAMP>data type, the value in field <SAMP>radix</SAMP>, which represents the base of the exponential representation, is equivalent to the symbolic constant <SAMP>FLT_RADIX</SAMP>.</P><P>For the types <SAMP>float, double</SAMP> and <SAMP>long double</SAMP> the value of <SAMP>epsilon</SAMP> is also available as <SAMP>FLT_EPSILON, DBL_EPSILON</SAMP>, and <SAMP>LDBL_EPSILON</SAMP>.</P><P>A NaN is a "Not a Number." It is a representable value that nevertheless does not correspond to any numeric quantity. Many numeric algorithms manipulate such values.</P><P>The IEC 559 standard is a standard approved by the International Electrotechnical Commission. It is the same as the IEEE standard 754.</P><P>Value returned by the function <SAMP>round_style()</SAMP> is one of the following: <SAMP>round_indeterminate, round_toward_zero, round_to_nearest, round_toward_infinity</SAMP>, or<SAMP> round_toward_neg_infinity.</SAMP></P><HR><A HREF="fun_3734.htm"><IMG SRC="images/prev.gif"></A> <A HREF="booktoc1.htm"><IMG SRC="images/toc.gif"></A><A HREF="tindex1.htm"><IMG SRC="images/next.gif"></A><P>©Copyright 1996, Rogue Wave Software, Inc.</P></BODY></HTML>⌨️ 快捷键说明
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