iostream.html

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</P>
<P>
<DL>
<DT><U>Method:</U> int <B>ios::fail</B> <I>() const</I>
<DD><A NAME="IDX20"></A>
Test for any kind of failure on this stream: <EM>either</EM> some
operation failed, <EM>or</EM> the stream is marked as bad.  (If either
<CODE>ios::failbit</CODE> or <CODE>ios::badbit</CODE> is set.)
</DL>

</P>
<P>
<DL>
<DT><U>Method:</U> void <B>ios::clear</B> <I>(iostate <VAR>state</VAR>)</I>
<DD><A NAME="IDX21"></A>
Set the state indication for this stream to the argument <VAR>state</VAR>.
You may call <CODE>ios::clear</CODE> with no argument, in which case the state
is set to <CODE>good</CODE> (no errors pending).

</P>
<P>
See <CODE>ios::good</CODE>, <CODE>ios::eof</CODE>, <CODE>ios::fail</CODE>, and
<CODE>ios::bad</CODE>, to test the state; see <CODE>ios::set</CODE> or
<CODE>ios::setstate</CODE> for an alternative way of setting the state.
</DL>

</P>


<H3><A NAME="SEC8" HREF="iostream_toc.html#TOC8">Choices in formatting</A></H3>

<P>
These methods control (or report on) settings for some details of
controlling streams, primarily to do with formatting output:

</P>
<P>
<DL>
<DT><U>Method:</U> char <B>ios::fill</B> <I>() const</I>
<DD><A NAME="IDX22"></A>
Report on the padding character in use.
</DL>

</P>
<P>
<DL>
<DT><U>Method:</U> char <B>ios::fill</B> <I>(char <VAR>padding</VAR>)</I>
<DD><A NAME="IDX23"></A>
Set the padding character.  You can also use the manipulator
<CODE>setfill</CODE>.  See section <A HREF="iostream.html#SEC9">Changing stream properties using manipulators</A>.

</P>
<P>
Default: blank.
</DL>

</P>
<P>
<DL>
<DT><U>Method:</U> int <B>ios::precision</B> <I>() const</I>
<DD><A NAME="IDX24"></A>
Report the number of significant digits currently in use for output of
floating point numbers.

</P>
<P>
Default: <CODE>6</CODE>.
</DL>

</P>
<P>
<DL>
<DT><U>Method:</U> int <B>ios::precision</B> <I>(int <VAR>signif</VAR>)</I>
<DD><A NAME="IDX25"></A>
Set the number of significant digits (for input and output numeric
conversions) to <VAR>signif</VAR>.

</P>
<P>
<A NAME="IDX26"></A>
<A NAME="IDX27"></A>
You can also use the manipulator <CODE>setprecision</CODE> for this purpose.
See section <A HREF="iostream.html#SEC9">Changing stream properties using manipulators</A>.
</DL>

</P>
<P>
<DL>
<DT><U>Method:</U> int <B>ios::width</B> <I>() const</I>
<DD><A NAME="IDX28"></A>
Report the current output field width setting (the number of
characters to write on the next <SAMP>`&#60;&#60;'</SAMP> output operation).

</P>
<P>
Default: <CODE>0</CODE>, which means to use as many characters as necessary.
</DL>

</P>
<P>
<DL>
<DT><U>Method:</U> int <B>ios::width</B> <I>(int <VAR>num</VAR>)</I>
<DD><A NAME="IDX29"></A>
Set the input field width setting to <VAR>num</VAR>.  Return the
<EM>previous</EM> value for this stream.

</P>
<P>
<A NAME="IDX30"></A>
<A NAME="IDX31"></A>
This value resets to zero (the default) every time you use <SAMP>`&#60;&#60;'</SAMP>; it is
essentially an additional implicit argument to that operator.  You can
also use the manipulator <CODE>setw</CODE> for this purpose.
See section <A HREF="iostream.html#SEC9">Changing stream properties using manipulators</A>.
</DL>

</P>
<P>
<DL>
<DT><U>Method:</U> fmtflags <B>ios::flags</B> <I>() const</I>
<DD><A NAME="IDX32"></A>
Return the current value of the complete collection of flags controlling
the format state.  These are the flags and their meanings when set:

</P>
<DL COMPACT>

<DT><CODE>ios::dec</CODE>
<DD>
<A NAME="IDX33"></A>
<DT><CODE>ios::oct</CODE>
<DD>
<A NAME="IDX34"></A>
<DT><CODE>ios::hex</CODE>
<DD>
<A NAME="IDX35"></A>
What numeric base to use in converting integers from internal to display
representation, or vice versa: decimal, octal, or hexadecimal,
respectively.  (You can change the base using the manipulator
<CODE>setbase</CODE>, or any of the manipulators <CODE>dec</CODE>, <CODE>oct</CODE>, or
<CODE>hex</CODE>; see section <A HREF="iostream.html#SEC9">Changing stream properties using manipulators</A>.)

On input, if none of these flags is set, read numeric constants
according to the prefix: decimal if no prefix (or a <SAMP>`.'</SAMP> suffix),
octal if a <SAMP>`0'</SAMP> prefix is present, hexadecimal if a <SAMP>`0x'</SAMP> prefix
is present.

Default: <CODE>dec</CODE>.

<DT><CODE>ios::fixed</CODE>
<DD>
<A NAME="IDX36"></A>
Avoid scientific notation, and always show a fixed number of digits after
the decimal point, according to the output precision in effect.
Use <CODE>ios::precision</CODE> to set precision.

<DT><CODE>ios::left</CODE>
<DD>
<A NAME="IDX37"></A>
<DT><CODE>ios::right</CODE>
<DD>
<A NAME="IDX38"></A>
<DT><CODE>ios::internal</CODE>
<DD>
<A NAME="IDX39"></A>
Where output is to appear in a fixed-width field; left-justified,
right-justified, or with padding in the middle (e.g. between a numeric
sign and the associated value), respectively.

<DT><CODE>ios::scientific</CODE>
<DD>
<A NAME="IDX40"></A>
Use scientific (exponential) notation to display numbers.

<DT><CODE>ios::showbase</CODE>
<DD>
<A NAME="IDX41"></A>
Display the conventional prefix as a visual indicator of the conversion
base: no prefix for decimal, <SAMP>`0'</SAMP> for octal, <SAMP>`0x'</SAMP> for hexadecimal.

<DT><CODE>ios::showpoint</CODE>
<DD>
<A NAME="IDX42"></A>
Display a decimal point and trailing zeros after it to fill out numeric
fields, even when redundant.

<DT><CODE>ios::showpos</CODE>
<DD>
<A NAME="IDX43"></A>
Display a positive sign on display of positive numbers.

<DT><CODE>ios::skipws</CODE>
<DD>
<A NAME="IDX44"></A>
Skip white space.  (On by default).

<DT><CODE>ios::stdio</CODE>
<DD>
<A NAME="IDX45"></A>
Flush the C <CODE>stdio</CODE> streams <CODE>stdout</CODE> and <CODE>stderr</CODE> after
each output operation (for programs that mix C and C++ output conventions).

<DT><CODE>ios::unitbuf</CODE>
<DD>
<A NAME="IDX46"></A>
Flush after each output operation.

<DT><CODE>ios::uppercase</CODE>
<DD>
<A NAME="IDX47"></A>
Use upper-case characters for the non-numeral elements in numeric
displays; for instance, <SAMP>`0X7A'</SAMP> rather than <SAMP>`0x7a'</SAMP>, or
<SAMP>`3.14E+09'</SAMP> rather than <SAMP>`3.14e+09'</SAMP>.
</DL>
</DL>

<P>
<DL>
<DT><U>Method:</U> fmtflags <B>ios::flags</B> <I>(fmtflags <VAR>value</VAR>)</I>
<DD><A NAME="IDX48"></A>
Set <VAR>value</VAR> as the complete collection of flags controlling the
format state.  The flag values are described under <SAMP>`ios::flags ()'</SAMP>.

</P>
<P>
Use <CODE>ios::setf</CODE> or <CODE>ios::unsetf</CODE> to change one property at a
time.
</DL>

</P>
<P>
<DL>
<DT><U>Method:</U> fmtflags <B>ios::setf</B> <I>(fmtflags <VAR>flag</VAR>)</I>
<DD><A NAME="IDX49"></A>
Set one particular flag (of those described for <SAMP>`ios::flags ()'</SAMP>;
return the complete collection of flags <EM>previously</EM> in effect.
(Use <CODE>ios::unsetf</CODE> to cancel.)
</DL>

</P>
<P>
<DL>
<DT><U>Method:</U> fmtflags <B>ios::setf</B> <I>(fmtflags <VAR>flag</VAR>, fmtflags <VAR>mask</VAR>)</I>
<DD><A NAME="IDX50"></A>
Clear the flag values indicated by <VAR>mask</VAR>, then set any of them that
are also in <VAR>flag</VAR>.  (Flag values are described for <SAMP>`ios::flags
()'</SAMP>.)  Return the complete collection of flags <EM>previously</EM> in
effect.  (See <CODE>ios::unsetf</CODE> for another way of clearing flags.)
</DL>

</P>
<P>
<DL>
<DT><U>Method:</U> fmtflags <B>ios::unsetf</B> <I>(fmtflags <VAR>flag</VAR>)</I>
<DD><A NAME="IDX51"></A>
Make certain <VAR>flag</VAR> (a combination of flag values described for
<SAMP>`ios::flags ()'</SAMP>) is not set for this stream; converse of
<CODE>ios::setf</CODE>.  Returns the old values of those flags.
</DL>

</P>


<H3><A NAME="SEC9" HREF="iostream_toc.html#TOC9">Changing stream properties using manipulators</A></H3>

<P>
For convenience, <VAR>manipulators</VAR> provide a way to change certain
properties of streams, or otherwise affect them, in the middle of
expressions involving <SAMP>`&#60;&#60;'</SAMP> or <SAMP>`&#62;&#62;'</SAMP>.  For example, you might
write

</P>

<PRE>
cout &#60;&#60; "|" &#60;&#60; setfill('*') &#60;&#60; setw(5) &#60;&#60; 234 &#60;&#60; "|";
</PRE>

<P>
to produce <SAMP>`|**234|'</SAMP> as output.

</P>
<P>
<DL>
<DT><U>Manipulator:</U>  <B>ws</B>
<DD><A NAME="IDX52"></A>
Skip whitespace.
</DL>

</P>
<P>
<DL>
<DT><U>Manipulator:</U>  <B>flush</B>
<DD><A NAME="IDX53"></A>
Flush an output stream.  For example, <SAMP>`cout &#60;&#60; ... &#60;&#60;flush;'</SAMP>
has the same effect as <SAMP>`cout &#60;&#60; ...; cout.flush();'</SAMP>.
</DL>

</P>
<P>
<DL>
<DT><U>Manipulator:</U>  <B>endl</B>
<DD><A NAME="IDX54"></A>
Write an end of line character <SAMP>`\n'</SAMP>, then flushes the output stream.
</DL>

</P>
<P>
<DL>
<DT><U>Manipulator:</U>  <B>ends</B>
<DD><A NAME="IDX55"></A>
Write <SAMP>`\0'</SAMP> (the string terminator character).
</DL>

</P>
<P>
<DL>
<DT><U>Manipulator:</U>  <B>setprecision</B> <I>(int <VAR>signif</VAR>)</I>
<DD><A NAME="IDX56"></A>
You can change the value of <CODE>ios::precision</CODE> in <SAMP>`&#60;&#60;'</SAMP>
expressions with the manipulator <SAMP>`setprecision(<VAR>signif</VAR>)'</SAMP>; for
example,

</P>

<PRE>
cout &#60;&#60; setprecision(2) &#60;&#60; 4.567;
</PRE>

<P>
prints <SAMP>`4.6'</SAMP>.  Requires <TT>`#include &#60;iomanip.h&#62;'</TT>.
</DL>

</P>
<P>
<DL>
<DT><U>Manipulator:</U>  <B>setw</B> <I>(int <VAR>n</VAR>)</I>
<DD><A NAME="IDX57"></A>
You can change the value of <CODE>ios::width</CODE> in <SAMP>`&#60;&#60;'</SAMP> expressions
with the manipulator <SAMP>`setw(<VAR>n</VAR>)'</SAMP>; for example,

</P>

<PRE>
cout &#60;&#60; setw(5) &#60;&#60; 234;
</PRE>

<P>
prints <SAMP>`  234'</SAMP> with two leading blanks.  Requires <TT>`#include
&#60;iomanip.h&#62;'</TT>.
</DL>

</P>
<P>
<DL>
<DT><U>Manipulator:</U>  <B>setbase</B> <I>(int <VAR>base</VAR>)</I>
<DD><A NAME="IDX58"></A>
Where <VAR>base</VAR> is one of <CODE>10</CODE> (decimal), <CODE>8</CODE> (octal), or
<CODE>16</CODE> (hexadecimal), change the base value for numeric
representations.  Requires <TT>`#include &#60;iomanip.h&#62;'</TT>.
</DL>

</P>
<P>
<DL>
<DT><U>Manipulator:</U>  <B>dec</B>
<DD><A NAME="IDX59"></A>
Select decimal base; equivalent to <SAMP>`setbase(10)'</SAMP>.
</DL>

</P>
<P>
<DL>
<DT><U>Manipulator:</U>  <B>hex</B>
<DD><A NAME="IDX60"></A>
Select hexadecimal base; equivalent to <SAMP>`setbase(16)'</SAMP>.
</DL>

</P>
<P>
<DL>
<DT><U>Manipulator:</U>  <B>oct</B>
<DD><A NAME="IDX61"></A>
Select octal base; equivalent to <SAMP>`setbase(8)'</SAMP>.
</DL>

</P>
<P>
<DL>
<DT><U>Manipulator:</U>  <B>setfill</B> <I>(char <VAR>padding</VAR>)</I>
<DD><A NAME="IDX62"></A>
Set the padding character, in the same way as <CODE>ios::fill</CODE>.
Requires <TT>`#include &#60;iomanip.h&#62;'</TT>.
</DL>

</P>


<H3><A NAME="SEC10" HREF="iostream_toc.html#TOC10">Extended data fields</A></H3>

<P>
A related collection of methods allows you to extend this collection of
flags and parameters for your own applications, without risk of conflict
between them:

</P>
<P>
<DL>
<DT><U>Method:</U> static fmtflags <B>ios::bitalloc</B> <I>()</I>
<DD><A NAME="IDX63"></A>
Reserve a bit (the single bit on in the result) to use as a flag.  Using
<CODE>bitalloc</CODE> guards against conflict between two packages that use
<CODE>ios</CODE> objects for different purposes.

</P>
<P>
This method is available for upward compatibility, but is not in the
ANSI working paper.  The number of bits available is limited; a
return value of <CODE>0</CODE> means no bit is available.
</DL>

</P>
<P>
<DL>
<DT><U>Method:</U> static int <B>ios::xalloc</B> <I>()</I>
<DD><A NAME="IDX64"></A>
Reserve space for a long integer or pointer parameter.  The result is a
unique nonnegative integer.  You can use it as an index to
<CODE>ios::iword</CODE> or <CODE>ios::pword</CODE>.  Use <CODE>xalloc</CODE> to arrange
for arbitrary special-purpose data in your <CODE>ios</CODE> objects, without
risk of conflict between packages designed for different purposes.
</DL>

</P>
<P>
<DL>
<DT><U>Method:</U> long&#38; <B>ios::iword</B> <I>(int <VAR>index</VAR>)</I>
<DD><A NAME="IDX65"></A>
Return a reference to arbitrary data, of long integer type, stored in an
<CODE>ios</CODE> instance.  <VAR>index</VAR>, conventionally returned from
<CODE>ios::xalloc</CODE>, identifies what particular data you need.
</DL>

</P>
<P>
<DL>
<DT><U>Method:</U> long <B>ios::iword</B> <I>(int <VAR>index</VAR>) const</I>
<DD><A NAME="IDX66"></A>
Return the actual value of a long integer stored in an <CODE>ios</CODE>.
</DL>

</P>
<P>
<DL>
<DT><U>Method:</U> void*&#38; <B>ios::pword</B> <I>(int <VAR>index</VAR>)</I>