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Subject: [Boost-commit] svn:boost r57671 - trunk/libs/format/doc
From: Samuel.Krempp_at_[hidden]
Date: 2009-11-15 03:02:50

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Author: samuel_krempp
Date: 2009-11-15 03:02:50 EST (Sun, 15 Nov 2009)
New Revision: 57671
URL: http://svn.boost.org/trac/boost/changeset/57671

Log:
reverting unintended modifications due to use of html editor
Text files modified:
trunk/libs/format/doc/format.html | 1782 +++++++++++++++++++++------------------
1 files changed, 943 insertions(+), 839 deletions(-)

Modified: trunk/libs/format/doc/format.html
==============================================================================
--- trunk/libs/format/doc/format.html (original)
+++ trunk/libs/format/doc/format.html 2009-11-15 03:02:50 EST (Sun, 15 Nov 2009)
@@ -1,102 +1,110 @@
-<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
-<HTML>
-<HEAD>
- <META HTTP-EQUIV="CONTENT-TYPE" CONTENT="text/html; charset=windows-1252">
- <TITLE>The Boost Format library</TITLE>
- <META NAME="GENERATOR" CONTENT="OpenOffice.org 3.1 (Win32)">
- <META NAME="CREATED" CONTENT="0;0">
- <META NAME="CHANGEDBY" CONTENT="Samuel K">
- <META NAME="CHANGED" CONTENT="20091115;8491800">
- <META HTTP-EQUIV="Content-Language" CONTENT="en-us">
- <STYLE TYPE="text/css">
- 
- </STYLE>
-</HEAD>
-<BODY LANG="fr-FR" TEXT="#000000" BGCOLOR="#ffffff" DIR="LTR">
-<H1><IMG SRC="../../../boost.png" NAME="images1" ALT="boost.png (6897 bytes)" ALIGN=MIDDLE WIDTH=277 HEIGHT=86 BORDER=0>The
-Boost Format library</H1>
-The <CODE><boost/format.hpp></CODE>
-format class provides printf-like formatting, in a type-safe manner
-which allows output of user-defined types.
-<UL>
- <LI>Synopsis
- 
- <LI><A HREF="#how_it_works">How it
- works</A>
- 
- <LI>Examples
- 
- <LI>Syntax
- 
- <UL>
- <LI><A HREF="#printf_directives">printf
- format-specification syntax</A>
- 
- <LI><A HREF="#printf_differences">Incompatibilities
- with printf</A>
- 
- </UL>
- <LI><A HREF="#manipulators">Manipulators
- and the internal stream state</A>
- 
- <LI><A HREF="#user-defined">User-defined
- types</A>
- 
- <LI>Alternatives
- 
- <LI>Exceptions
- 
- <LI>Performance
- 
- <LI><A HREF="#extract">Class Interface
- Extract</A>
- 
- <LI>Rationale
- 
-</UL>
-<HR>
-<H2>Synopsis</H2>
-A format object is constructed from a format-string, and is then
-given arguments through repeated calls to operator%. Each
-of those arguments are then converted to strings, who are in turn
-combined into one string, according to the format-string.
-<PRE STYLE="margin-left: 1cm; margin-right: 1cm">cout << boost::format("writing %1%, x=%2% : %3%-th try") % "toto" % 40.23 % 50;
- // prints "writing toto, x=40.230 : 50-th try"</PRE>
-<HR>
-<H2>How it works</H2>
-<OL>
- <LI>When you call format(s),
- where s is the format-string, it constructs an object, which parses
- the format string and look for all directives in it and prepares
- internal structures for the next step.
- 
- <LI>Then, either immediately, as in
- 
- <PRE STYLE="margin-right: 1cm; margin-bottom: 0.5cm">cout << format("%2% %1%") % 36 % 77;</PRE>
- or later on, as in
- 
- <PRE STYLE="margin-right: 1cm">format fmter("%2% %1%");
-fmter % 36; fmter % 77;</PRE>
- you feed variables into the formatter. those variables are
- dumped into an internal stream, which state is set according to the
- given formatting options in the format-string -if there are any-,
- and the format object stores the string results for the last step.
- 
- <LI>Once all arguments have been fed you can dump the format
- object to a stream, or get its string value by using the str()
- member function, or the free function str(const format& )
- in namespace boost. The result string stays accessible in the
- format object until another argument is passed, at which time it is
- reinitialised.
- 
- <PRE STYLE="margin-right: 1cm">
+<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
+
+<html>
+<head>
+ <meta http-equiv="Content-Language" content="en-us">
+ <meta http-equiv="Content-Type" content="text/html; charset=us-ascii">
+
+ <title>The Boost Format library</title>
+</head>
+
+<body bgcolor="white" text="black">
+ <h1><img align="middle" alt="boost.png (6897 bytes)" height="86" src=
+ "../../../boost.png" width="277">The Boost Format library</h1>
+
+ The <code><a href=
+ "../../../boost/format.hpp"><boost/format.hpp></a></code> format
+ class provides printf-like formatting, in a type-safe manner which allows
+ output of user-defined types. 
+
+ <ul>
+ <li>Synopsis</li>
+
+ <li>How it works</li>
+
+ <li>Examples</li>
+
+ <li>
+ Syntax
+
+ <ul>
+ <li><a href="#printf_directives">printf format-specification
+ syntax</a></li>
+
+ <li><a href="#printf_differences">Incompatibilities with
+ printf</a></li>
+ </ul>
+ </li>
+
+ <li><a href="#manipulators">Manipulators and the internal stream
+ state</a></li>
+
+ <li>User-defined types</li>
+
+ <li>Alternatives</li>
+
+ <li>Exceptions</li>
+
+ <li>Performance</li>
+
+ <li>Class Interface Extract</li>
+
+ <li>Rationale</li>
+ </ul><a name="synopsis" id="synopsis"></a>
+ <hr>
+
+ <h2>Synopsis</h2>
+
+ A format object is constructed from a format-string, and is then given
+ arguments through repeated calls to operator%. 
+ Each of those arguments are then converted to strings, who are in turn
+ combined into one string, according to the format-string.
+
+ <blockquote>
+ <pre>
+cout << boost::format("writing %1%, x=%2% : %3%-th try") % "toto" % 40.23 % 50;
+ // prints "writing toto, x=40.230 : 50-th try"
+</pre>
+ </blockquote><a name="how_it_works" id="how_it_works"></a>
+ <hr>
+
+ <h2>How it works</h2>
+
+ <ol>
+ <li>When you call format(s), where s is the format-string, it
+ constructs an object, which parses the format string and look for all
+ directives in it and prepares internal structures for the next step.</li>
+
+ <li>Then, either immediately, as in
+
+ <blockquote>
+ <pre>
+cout << format("%2% %1%") % 36 % 77;
+</pre>
+ </blockquote>or later on, as in
+
+ <blockquote>
+ <pre>
+format fmter("%2% %1%");
+fmter % 36; fmter % 77;
+</pre>
+ </blockquote>you feed variables into the formatter. 
+ those variables are dumped into an internal stream, which state is set
+ according to the given formatting options in the format-string -if
+ there are any-, and the format object stores the string results for the
+ last step.
+ </li>
+
+ <li>Once all arguments have been fed you can dump the format object to a
+ stream, or get its string value by using the str() member
+ function, or the free function str(const format& ) in
+ namespace boost. The result string stays accessible in the format
+ object until another argument is passed, at which time it is
+ reinitialised.
+
+ <blockquote>
+ <pre>
+
// fmter was previously created and fed arguments, it can print the result :
cout << fmter ;

@@ -107,711 +115,793 @@
s = fmter.str( );

// You can also do all steps at once :
-cout << boost::format("%2% %1%") % 36 % 77;
+cout << boost::format("%2% %1%") % 36 % 77;

// using the str free function :
-string s2 = str( format("%2% %1%") % 36 % 77 );
-</PRE>
- <LI>Optionnally, after step 3, you can re-use a format object and
- restart at step2 : fmter % 18 % 39; to format new
- variables with the same format-string, saving the expensive
- processing involved at step 1.
- 
-</OL>
-All in all, the format class translates
-a format-string (with eventually printf-like directives) into
-operations on an internal stream, and finally returns the result of
-the formatting, as a string, or directly into an output stream.
-
-<HR>
-<H2>Examples</H2>
-<PRE STYLE="margin-left: 1cm; margin-right: 1cm">using namespace std;
+string s2 = str( format("%2% %1%") % 36 % 77 );
+
+</pre>
+ </blockquote>
+ </li>
+
+ <li>Optionnally, after step 3, you can re-use a format object and restart
+ at step2 : fmter % 18 % 39; 
+ to format new variables with the same format-string, saving the expensive
+ processing involved at step 1.</li>
+ </ol>All in all, the format class translates a format-string (with
+ eventually printf-like directives) into operations on an internal stream,
+ and finally returns the result of the formatting, as a string, or directly
+ into an output stream. <a name="examples" id="examples"></a>
+ <hr>
+
+ <h2>Examples</h2>
+
+ <blockquote>
+ <pre>
+using namespace std;
using boost::format;
-using boost::io::group;</PRE>
-<UL>
- <LI>Simple output, with reordering :
- 
- <PRE STYLE="margin-right: 1cm">
-cout << format("%1% %2% %3% %2% %1% \n") % "11" % "22" % "333"; // 'simple' style.
-</PRE>
- It prints : "11 22 333 22 11 \n"
- 
- <LI>More precise formatting, with Posix-printf positional
- directives :
- 
- <PRE STYLE="margin-right: 1cm">
-cout << format("(x,y) = (%1$+5d,%2$+5d) \n") % -23 % 35; // Posix-Printf style
-</PRE>
- It prints : "(x,y) = ( -23, +35) \n"
- 
- <LI>classical printf directive, no reordering :
- 
- <PRE STYLE="margin-right: 1cm">
-cout << format("writing %s, x=%s : %d-th step \n") % "toto" % 40.23 % 50;
-</PRE>
- It prints : "writing toto, x=40.23 : 50-th step \n"
- 
- <LI>Several ways to express the same thing :
- 
- <PRE STYLE="margin-right: 1cm">
-cout << format("(x,y) = (%+5d,%+5d) \n") % -23 % 35;
-cout << format("(x,y) = (%|+5|,%|+5|) \n") % -23 % 35;
-
-cout << format("(x,y) = (%1$+5d,%2$+5d) \n") % -23 % 35;
-cout << format("(x,y) = (%|1$+5|,%|2$+5|) \n") % -23 % 35;
-</PRE>
- all those print : "(x,y) = ( -23, +35) \n"
- 
- <LI>Using manipulators to modify the format-string :
- 
- <PRE STYLE="margin-right: 1cm">
-format fmter("_%1$+5d_ %1$d \n");
+using boost::io::group;
+</pre>
+ </blockquote>
+
+ <ul>
+ <li>Simple output, with reordering :
+
+ <blockquote>
+ <pre>
+
+cout << format("%1% %2% %3% %2% %1% \n") % "11" % "22" % "333"; // 'simple' style.
+
+</pre>
+ </blockquote>It prints : "11 22 333 22 11 \n"
+ </li>
+
+ <li>More precise formatting, with Posix-printf positional directives :
+
+ <blockquote>
+ <pre>
+
+cout << format("(x,y) = (%1$+5d,%2$+5d) \n") % -23 % 35; // Posix-Printf style
+
+</pre>
+ </blockquote>It prints : "(x,y) = ( -23, +35) \n"
+ </li>
+
+ <li>classical printf directive, no reordering :
+
+ <blockquote>
+ <pre>
+
+cout << format("writing %s, x=%s : %d-th step \n") % "toto" % 40.23 % 50;

-format fmter2("_%1%_ %1% \n");
+</pre>
+ </blockquote>It prints : "writing toto, x=40.23 : 50-th step \n"
+ </li>
+
+ <li>Several ways to express the same thing :
+
+ <blockquote>
+ <pre>
+
+cout << format("(x,y) = (%+5d,%+5d) \n") % -23 % 35;
+cout << format("(x,y) = (%|+5|,%|+5|) \n") % -23 % 35;
+
+cout << format("(x,y) = (%1$+5d,%2$+5d) \n") % -23 % 35;
+cout << format("(x,y) = (%|1$+5|,%|2$+5|) \n") % -23 % 35;
+
+</pre>
+ </blockquote>all those print : "(x,y) = ( -23, +35) \n"
+ </li>
+
+ <li>Using manipulators to modify the format-string :
+
+ <blockquote>
+ <pre>
+
+format fmter("_%1$+5d_ %1$d \n");
+
+format fmter2("_%1%_ %1% \n");
fmter2.modify_item(1, group(showpos, setw(5)) );

cout << fmter % 101 ;
cout << fmter2 % 101 ;
-</PRE>
- Both print the same : "_ +101_ 101 \n"
- 
- <LI>Using manipulators with arguments :
- 
- <PRE STYLE="margin-right: 1cm">
-cout << format("_%1%_ %1% \n") % group(showpos, setw(5), 101);
-</PRE>
- The manipulators are applied at each occurence of %1%, and thus it
- prints : "_ +101_ +101 \n"
- 
- <LI>New formatting feature : 'absolute tabulations', useful
- inside loops, to insure a field is printed at the same position from
- one line to the next, even if the widthes of the previous arguments
- can vary a lot.
- 
- <PRE STYLE="margin-right: 1cm">
+
+</pre>
+ </blockquote>Both print the same : "_ +101_ 101 \n"
+ </li>
+
+ <li>Using manipulators with arguments :
+
+ <blockquote>
+ <pre>
+
+cout << format("_%1%_ %1% \n") % group(showpos, setw(5), 101);
+
+</pre>
+ </blockquote>The manipulators are applied at each occurence of %1%, and
+ thus it prints : "_ +101_ +101 \n"
+ </li>
+
+ <li>New formatting feature : 'absolute tabulations', useful inside loops,
+ to insure a field is printed at the same position from one line to the
+ next, even if the widthes of the previous arguments can vary a lot.
+
+ <blockquote>
+ <pre>
+
for(unsigned int i=0; i < names.size(); ++i)
- cout << format("%1%, %2%, %|40t|%3%\n") % names[i] % surname[i] % tel[i];
-</PRE>
- For some std::vector names, surnames, and tel
- (see sample_new_features.cpp) it prints :
- 
- <PRE STYLE="margin-right: 1cm">Marc-François Michel, Durand, +33 (0) 123 456 789
-Jean, de Lattre de Tassigny, +33 (0) 987 654 321</PRE>
-</UL>
-<HR>
-<H2>Sample Files</H2>
-The program sample_formats.cpp
-demonstrates simple uses of format.
-sample_new_features.cpp
-illustrates the few formatting features that were added to printf's
-syntax such as simple positional directives, centered alignment, and
-'tabulations'.
-sample_advanced.cpp
-demonstrates uses of advanced features, like reusing, and modifying,
-format objects, etc..
-And sample_userType.cpp
-shows the behaviour of the format library on user-defined
-types.
-<HR>
-<H2>Syntax</H2>
-boost::format( format-string ) % arg1 % arg2
-% ... % argN
-The format-string contains text in which special directives
-will be replaced by strings resulting from the formatting of the
-given arguments. The legacy syntax in the C and C++ worlds is the
-one used by printf, and thus format can use directly printf
-format-strings, and produce the same result (in almost all cases. see
-Incompatibilities with printf for
-details) This core syntax was extended, to allow new features, but
-also to adapt to the C++ streams context. Thus, format accepts
-several forms of directives in format-strings :
-<UL>
- <LI>Legacy printf format strings :
- %spec where spec is a <A HREF="#printf_directives">printf
- format specification</A> spec passes formatting options,
- like width, alignment, numerical base used for formatting numbers,
- as well as other specific flags. But the classical
- type-specification flag of printf has a weaker meaning in
- format. It merely sets the appropriate flags on the internal stream,
- and/or formatting parameters, but does not require the corresponding
- argument to be of a specific type. e.g. : the specification 2$x,
- meaning "print argument number 2, which is an integral number,
- in hexa" for printf, merely means "print argument 2 with
- stream basefield flags set to hex" for format.
- 
- <LI>%|spec| where
- spec is a printf format specification. The enclosing pipes
- are introduced, to improve the readability of the format-string, but
- primarily, to make the type-conversion character optional in
- spec. This information is not necessary with C++ variables,
- but with direct printf syntax, it is necessary to always give a
- type-conversion character, merely because this character is crucial
- to determine the end of a format-specification. e.g. : "%|-5|"
- will format the next variable with width set to 5, and
- left-alignment just like the following printf directives : "%-5g",
- "%-5f", "%-5s" ..
- 
- <LI>%N% This simple positional notation
- requests the formatting of the N-th argument - wihout any
- formatting option. (It's merely a shortcut to Printf's positional
- directives (like "%N$s"), but a major benefit is
- that it's much more readable, and does not use a "type-conversion"
- character)
- 
-</UL>
-On top of the standard printf format specifications, new features
-were implemented, like centered alignment. See <A HREF="#new_directives">new
-format specification</A> for details.
-
-<H3>printf format specifications</H3>
-The printf format specifications supported by Boost.format follows
-the Unix98 <A HREF="http://www.opengroup.org/onlinepubs/7908799/xsh/fprintf.html">Open-group
-printf</A> precise syntax, rather than the standard C printf, which
-does not support positional arguments. (Common flags have the same
-meaning in both, so it should not be a headache for anybody) Note
-that it is an error to use positional format specifications (e.g.
-%3$+d) mixed with non-positional ones (e.g. %+d)
-in the same format string. In the Open-group specification,
-referring to the same argument several times (e.g. "%1$d
-%1$d") has undefined behaviour. Boost.format's behaviour in
-such cases is to allow each argument to be reffered to any number of
-times. The only constraint is that it expects exactly P
-arguments, P being the maximum argument number used in the
-format string. (e.g., for "%1$d %10$d", P == 10
-). Supplying more, or less, than P arguments raises an
-exception. (unless it was set otherwise, see exceptions)
- A specification spec has the form : [ N$
-] [ flags ] [ width ] [ . precision ]
-type-char Fields insided square brackets are optional.
-Each of those fields are explained one by one in the following list :
-<UL>
- <LI>N $ (optional field)
- specifies that the format specification applies to the N-th
- argument. (it is called a positional format specification) If
- this is not present, arguments are taken one by one. (and it is then
- an error to later supply an argument number)
- 
- <LI>flags is a sequences of any of those :
- 
- <TABLE BORDER=1 CELLPADDING=5 CELLSPACING=2>
- <TR>
- <TD>
- Flag
- </TD>
- <TD>
- Meaning
- </TD>
- <TD>
- effect on internal stream
- </TD>
- </TR>
- <TR>
- <TD>
- '-'
- </TD>
- <TD>
- left alignment
- </TD>
- <TD>
- N/A (applied later on the string)
- </TD>
- </TR>
- <TR>
- <TD>
- '='
- </TD>
- <TD>
- centered alignment
- </TD>
- <TD>
- N/A (applied later on the string) - note : added
- feature, not in printf -
- </TD>
- </TR>
- <TR>
- <TD>
- '_'
- </TD>
- <TD>
- internal alignment
- </TD>
- <TD>
- sets internal alignment - note : added feature, not in
- printf -
- </TD>
- </TR>
- <TR>
- <TD>
- '+'
- </TD>
- <TD>
- show sign even for positive numbers
- </TD>
- <TD>
- sets showpos
- </TD>
- </TR>
- <TR>
- <TD>
- '#'
- </TD>
- <TD>
- show numerical base, and decimal point
- </TD>
- <TD>
- sets showbase and showpoint
- </TD>
- </TR>
- <TR>
- <TD>
- '0'
- </TD>
- <TD>
- pad with 0's (inserted after sign or base indicator)
- </TD>
- <TD>
- if not left-aligned, calls setfill('0') and sets
- internal Extra actions are taken after stream
- conversion to handle user-defined output.
- </TD>
- </TR>
- <TR>
- <TD>
- ' '
- </TD>
- <TD>
- if the string does not begin with + or -, insert
- a space before the converted string
- </TD>
- <TD>
- N/A (applied later on the string) Different to printf's
- behaviour : it is not affected by internal alignment
- </TD>
- </TR>
- </TABLE>
- <LI>width specifies a minimal
- width for the string resulting form the conversion. If necessary,
- the string will be padded with alignment and fill characters either
- set on the stream via manipulators, or specified by the
- format-string (e.g. flags '0', '-', ..) Note that width is not
- just set on the conversion stream. To support output of <A HREF="#user-defined">user-defined
- types</A> (that might call operator<< many times on
- several members), the width is handled after stream conversion of
- the whole argument object, in the format class code.
- 
- <LI>precision (preceded by a
- point), sets the stream's precision
- 
- <UL>
- <LI>When outputting a floatting type
- number, it sets the maximum number of digits
- 
- <UL>
- <LI>after decimal point when in
- fixed or scientific mode
- 
- <LI>in total when in default mode
- ('general mode', like %g)
- 
- </UL>
- <LI>When used with type-char s
- or S it takes another meaning : the conversion string is
- truncated to the precision first chars. (Note that the
- eventual padding to width is done after truncation.)
- 
- </UL>
- <LI>type-char. it does not impose the concerned
- argument to be of a restricted set of types, but merely sets the
- flags that are associated with this type specification.
- 
- <TABLE BORDER=1 CELLPADDING=5 CELLSPACING=2>
- <TR>
- <TD>
- Type-Char
- </TD>
- <TD>
- Meaning
- </TD>
- <TD>
- effect on stream
- </TD>
- </TR>
- <TR>
- <TD>
- p or x
- </TD>
- <TD>
- hexadecimal output
- </TD>
- <TD>
- sets hex
- </TD>
- </TR>
- <TR>
- <TD>
- o
- </TD>
- <TD>
- octal output
- </TD>
- <TD>
- sets oct
- </TD>
- </TR>
- <TR>
- <TD>
- e
- </TD>
- <TD>
- scientific float format
- </TD>
- <TD>
- sets floatfield bits to scientific
- </TD>
- </TR>
- <TR>
- <TD>
- f
- </TD>
- <TD>
- fixed float format
- </TD>
- <TD>
- sets floatfield bits to fixed
- </TD>
- </TR>
- <TR>
- <TD>
- g
- </TD>
- <TD>
- general -default- float format
- </TD>
- <TD>
- unset all floatfield bits
- </TD>
- </TR>
- <TR>
- <TD>
- X, E or G
- </TD>
- <TD>
- same effect as their lowercase counterparts, but using
- uppercase letters for number outputs. (exponents, hex digits, ..)
- </TD>
- <TD>
- same effects as 'x', 'e', or 'g', plus
- uppercase
- </TD>
- </TR>
- <TR>
- <TD>
- d, i or u
- </TD>
- <TD>
- decimal type output
- </TD>
- <TD>
- sets basefield bits to dec
- </TD>
- </TR>
- <TR>
- <TD>
- s or S
- </TD>
- <TD>
- string output
- </TD>
- <TD>
- precision specification is unset, and its value goes to
- an internal field for later 'truncation'. (see precision
- explanation above)
- </TD>
- </TR>
- <TR>
- <TD>
- c or C
- </TD>
- <TD>
- 1-character output
- </TD>
- <TD>
- only the first character of the conversion string is used.
- </TD>
- </TR>
- <TR>
- <TD>
- %
- </TD>
- <TD>
- print the character %
- </TD>
- <TD>
- N/A
- </TD>
- </TR>
- </TABLE>
- Note that the 'n' type specification is ignored (and so is the
- corresponding argument), because it does not fit in this
- context. Also, printf 'l', 'L', or 'h' modifiers (to indicate
- wide, long or short types) are supported (and simply have no effect
- on the internal stream).
-</UL>
-<H3><A NAME="new_directives"></A>new format-specifications</H3>
-<UL>
- <LI>as stated in the flags table,
- centered and internal alignment flags (' = ', and ' _
- ') were added.
- 
- <LI>%|nt|
- , where n is a positive number, inserts an absolute
- tabulation. It means that format will, if needed, fill the
- string with characters, until the length of the string created so
- far reaches n characters. (see examples
- )
- 
- <LI>%|nTX| inserts a
- tabulation in the same way, but using X as fill character
- instead of the current 'fill' char of the stream (which is space
- for a stream in default state)
- 
-</UL>
-<H2><A NAME="printf_differences"></A>Differences of behaviour vs
-printf</H2>
-Suppose you have variables x1, x2 (built_in types,
-supported by C's printf), and a format string s intended
-for use with a printf function this way :
-
-<PRE STYLE="margin-left: 1cm; margin-right: 1cm; margin-bottom: 0.5cm">printf(s, x1, x2);</PRE>
- In almost all cases, the result will be the same as with this
-command :
-
-<PRE STYLE="margin-left: 1cm; margin-right: 1cm; margin-bottom: 0.5cm">cout << format(s) % x1 % x2;</PRE>
-But because some printf format specifications don't translate well
-into stream formatting options, there are a few notable imperfections
-in the way Boost.format emulates printf. In any case, the format
-class should quietly ignore the unsupported options, so that printf
-format-strings are always accepted by format and produce almost the
-same output as printf.
- Here is the full list of such differences :
-
-<UL>
- <LI>'0' and ' ' options
- : printf ignores these options for non numeric conversions, but
- format applies them to all types of variables. (so it is possible to
- use those options on user-defined types, e.g. a Rational class,
- etc..)
- 
- <LI>precision for integral
- types arguments has a special meaning for printf : printf(
- "(%5.3d)" , 7 ) ; prints « ( 007) » While
- format, like streams, ignores the precision parameter for integral
- types conversions.
- 
- <LI>the ' printf option (format
- with thousands grouping characters)) has no effect in format.
- 
- <LI>Width or precision set to asterisk (*) are used by
- printf to read this field from an argument. e.g.
- printf("%1$d:%2$.*3$d:%4$.*3$d\n", hour, min,
- precision, sec); This class does not support this mechanism
- for now. so such precision or width fields are quietly ignored by
- the parsing.
- 
-</UL>
-Also, note that the special 'n' type-specification (used to
-tell printf to save in a variable the number of characters output by
-the formatting) has no effect in format. Thus format strings
-containing this type-specification should produce the same converted
-string by printf or format. It will not cause differences in the
-formatted strings between printf and format. To get the number of
-characters in the formatted string using Boost.Format, you can use
-the size() member function :
-
-<PRE STYLE="margin-left: 1cm; margin-right: 1cm">format formatter("%+5d");
+ cout << format("%1%, %2%, %|40t|%3%\n") % names[i] % surname[i] % tel[i];
+
+</pre>
+ </blockquote>For some std::vector names, surnames, and
+ tel (see sample_new_features.cpp) it prints :
+
+ <blockquote>
+ <pre>
+Marc-François Michel, Durand, +33 (0) 123 456 789
+Jean, de Lattre de Tassigny, +33 (0) 987 654 321
+</pre>
+ </blockquote>
+ </li>
+ </ul>
+ <hr>
+
+ <h2>Sample Files</h2>
+
+ The program <a href=
+ "../example/sample_formats.cpp">sample_formats.cpp</a> demonstrates simple
+ uses of format. 
+
+ sample_new_features.cpp
+ illustrates the few formatting features that were added to printf's syntax
+ such as simple positional directives, centered alignment, and
+ 'tabulations'. 
+
+ sample_advanced.cpp
+ demonstrates uses of advanced features, like reusing, and modifying, format
+ objects, etc.. 
+
+ And sample_userType.cpp
+ shows the behaviour of the format library on user-defined
+ types.<a name="syntax" id="syntax"></a>
+ <hr>
+
+ <h2>Syntax</h2>
+
+ boost::format( format-string ) % arg1 % arg2
+ % ... % argN
+
+ The format-string contains text in which special directives will
+ be replaced by strings resulting from the formatting of the given
+ arguments. 
+ The legacy syntax in the C and C++ worlds is the one used by printf, and
+ thus format can use directly printf format-strings, and produce the same
+ result (in almost all cases. see <a href=
+ "#printf_differences">Incompatibilities with printf</a> for details) 
+ This core syntax was extended, to allow new features, but also to adapt to
+ the C++ streams context. Thus, format accepts several forms of directives
+ in format-strings :
+
+ <ul>
+ <li>Legacy printf format strings : %spec where spec
+ is a printf format specification 
+ spec passes formatting options, like width, alignment, numerical
+ base used for formatting numbers, as well as other specific flags. But
+ the classical type-specification flag of printf has a weaker
+ meaning in format. It merely sets the appropriate flags on the internal
+ stream, and/or formatting parameters, but does not require the
+ corresponding argument to be of a specific type. 
+ e.g. : the specification 2$x, meaning "print argument number 2,
+ which is an integral number, in hexa" for printf, merely means "print
+ argument 2 with stream basefield flags set to hex" for
+ format.</li>
+
+ <li>%|spec| where spec is a printf format
+ specification. 
+ This pipe-delimited syntax is introduced, to improve the readability of the
+ format-string, but primarily, to make the type-conversion
+ character optional in spec. This information is not necessary
+ with C++ variables, but with direct printf syntax, it is necessary to
+ always give a type-conversion character, merely because this character is
+ crucial to determine the end of a format-specification. 
+ e.g. : "%|-5|" will format the next variable with width set to 5, and
+ left-alignment just like the following printf directives : "%-5g",
+ "%-5f", "%-5s" ..</li>
+
+ <li>%N% 
+ This simple positional notation requests the formatting of the
+ N-th argument - wihout any formatting option. 
+ (It's merely a shortcut to Printf's positional directives (like
+ "%N$s"), but a major benefit is that it's much more readable, and
+ does not use a "type-conversion" character)</li>
+ </ul>On top of the standard printf format specifications, new features were
+ implemented, like centered alignment. See <a href="#new_directives">new
+ format specification</a> for details. <a name="printf_directives" id=
+ "printf_directives"></a>
+
+ <h3>printf format specifications</h3>
+
+ The printf format specifications supported by Boost.format follows the
+ Unix98 <a href=
+ "http://www.opengroup.org/onlinepubs/7908799/xsh/fprintf.html">Open-group
+ printf</a> precise syntax, rather than the standard C printf, which does
+ not support positional arguments. (Common flags have the same meaning in
+ both, so it should not be a headache for anybody) 
+ Note that it is an error to use positional format specifications
+ (e.g. %3$+d) mixed with non-positional ones (e.g. %+d)
+ in the same format string. 
+ In the Open-group specification, referring to the same argument several
+ times (e.g. "%1$d %1$d") has undefined behaviour. Boost.format's
+ behaviour in such cases is to allow each argument to be reffered to any
+ number of times. The only constraint is that it expects exactly P
+ arguments, P being the maximum argument number used in the format
+ string. (e.g., for "%1$d %10$d", P == 10 ). 
+ Supplying more, or less, than P arguments raises an exception.
+ (unless it was set otherwise, see exceptions)
+
+ 
+ 
+ A specification spec has the form : [ N$ ] [
+ flags ] [ width ] [ . precision ]
+ type-char 
+ 
+ Fields insided square brackets are optional. Each of those fields are
+ explained one by one in the following list :
+
+ <ul>
+ <li>N $ (optional field) specifies that the format
+ specification applies to the N-th argument. (it is called a
+ positional format specification) 
+ If this is not present, arguments are taken one by one. (and it is then
+ an error to later supply an argument number)</li>
+
+ <li>
+ flags is a sequences of any of those :
+
+ <blockquote>
+ <table border="1" cellpadding="5" summary="">
+ <tr>
+ <td>Flag</td>
+
+ <td>Meaning</td>
+
+ <td>effect on internal stream</td>
+ </tr>
+
+ <tr>
+ <td>'-'</td>
+
+ <td>left alignment</td>
+
+ <td>N/A (applied later on the string)</td>
+ </tr>
+
+ <tr>
+ <td>'='</td>
+
+ <td>centered alignment</td>
+
+ <td>N/A (applied later on the string) 
+ - note : added feature, not in printf -</td>
+ </tr>
+
+ <tr>
+ <td>'_'</td>
+
+ <td>internal alignment</td>
+
+ <td>sets internal alignment 
+ - note : added feature, not in printf -</td>
+ </tr>
+
+ <tr>
+ <td>'+'</td>
+
+ <td>show sign even for positive numbers</td>
+
+ <td>sets showpos</td>
+ </tr>
+
+ <tr>
+ <td>'#'</td>
+
+ <td>show numerical base, and decimal point</td>
+
+ <td>sets showbase and showpoint</td>
+ </tr>
+
+ <tr>
+ <td>'0'</td>
+
+ <td>pad with 0's (inserted after sign or base indicator)</td>
+
+ <td>if not left-aligned, calls setfill('0') and sets
+ internal 
+ Extra actions are taken after stream conversion to handle
+ user-defined output.</td>
+ </tr>
+
+ <tr>
+ <td>' '</td>
+
+ <td>if the string does not begin with + or -,
+ insert a space before the converted string</td>
+
+ <td>N/A (applied later on the string) 
+ Different to printf's behaviour : it is not affected by internal
+ alignment</td>
+ </tr>
+ </table>
+ </blockquote>
+ </li>
+
+ <li>width specifies a minimal width for the string resulting form
+ the conversion. If necessary, the string will be padded with alignment
+ and fill characters either set on the stream via manipulators, or
+ specified by the format-string (e.g. flags '0', '-', ..) 
+ Note that width is not just set on the conversion stream. To support
+ output of user-defined types (that might call
+ operator<< many times on several members), the width is
+ handled after stream conversion of the whole argument object, in the
+ format class code.</li>
+
+ <li>
+ precision (preceded by a point), sets the stream's
+ precision
+
+ <ul>
+ <li>When outputting a floatting type number, it sets the maximum
+ number of digits
+
+ <ul>
+ <li>after decimal point when in fixed or scientific mode</li>
+
+ <li>in total when in default mode ('general mode', like
+ %g)</li>
+ </ul>
+ </li>
+
+ <li>When used with type-char s or S it takes another
+ meaning : the conversion string is truncated to the precision
+ first chars. (Note that the eventual padding to width is done
+ after truncation.)</li>
+ </ul>
+ </li>
+
+ <li>
+ type-char. it does not impose the concerned argument to
+ be of a restricted set of types, but merely sets the flags that are
+ associated with this type specification.
+
+ <blockquote>
+ <table border="1" cellpadding="5" summary="">
+ <tr>
+ <td>Type-Char</td>
+
+ <td>Meaning</td>
+
+ <td>effect on stream</td>
+ </tr>
+
+ <tr>
+ <td>p or x</td>
+
+ <td>hexadecimal output</td>
+
+ <td>sets hex</td>
+ </tr>
+
+ <tr>
+ <td>o</td>
+
+ <td>octal output</td>
+
+ <td>sets oct</td>
+ </tr>
+
+ <tr>
+ <td>e</td>
+
+ <td>scientific float format</td>
+
+ <td>sets floatfield bits to scientific</td>
+ </tr>
+
+ <tr>
+ <td>f</td>
+
+ <td>fixed float format</td>
+
+ <td>sets floatfield bits to fixed</td>
+ </tr>
+
+ <tr>
+ <td>g</td>
+
+ <td>general -default- float format</td>
+
+ <td>unset all floatfield bits</td>
+ </tr>
+
+ <tr>
+ <td>X, E or G</td>
+
+ <td>same effect as their lowercase counterparts, but using
+ uppercase letters for number outputs. (exponents, hex digits,
+ ..)</td>
+
+ <td>same effects as 'x', 'e', or 'g',
+ plus uppercase</td>
+ </tr>
+
+ <tr>
+ <td>d, i or u</td>
+
+ <td>decimal type output</td>
+
+ <td>sets basefield bits to dec</td>
+ </tr>
+
+ <tr>
+ <td>s or S</td>
+
+ <td>string output</td>
+
+ <td>precision specification is unset, and its value goes
+ to an internal field for later 'truncation'. (see
+ precision explanation above)</td>
+ </tr>
+
+ <tr>
+ <td>c or C</td>
+
+ <td>1-character output</td>
+
+ <td>only the first character of the conversion string is
+ used.</td>
+ </tr>
+
+ <tr>
+ <td>%</td>
+
+ <td>print the character %</td>
+
+ <td>N/A</td>
+ </tr>
+ </table>
+ </blockquote>
+
+ Note that the 'n' type specification is ignored (and so is the
+ corresponding argument), because it does not fit in this context. 
+ Also, printf 'l', 'L', or 'h' modifiers (to indicate wide, long or
+ short types) are supported (and simply have no effect on the internal
+ stream).
+ </li>
+ </ul><a name="new_directives" id="new_directives"></a>
+
+ <h3>new format-specifications</h3>
+
+ <ul>
+ <li>as stated in the flags table, centered and internal alignment flags
+ (' = ', and ' _ ') were added.</li>
+
+ <li>%{nt} , where n is a positive number,
+ inserts an absolute tabulation. It means that format will, if
+ needed, fill the string with characters, until the length of the string
+ created so far reaches n characters. (see <a href=
+ "#examples">examples</a> )</li>
+
+ <li>%|nTX| inserts a tabulation in the
+ same way, but using X as fill character instead of the current
+ 'fill' char of the stream (which is space for a stream in default
+ state)</li>
+ </ul><a name="printf_differences" id="printf_differences"></a>
+
+ <h2>Differences of behaviour vs printf</h2>Suppose you have variables
+ x1, x2 (built_in types, supported by C's printf), 
+ and a format string s intended for use with a printf function this
+ way :
+
+ <blockquote>
+ <pre>
+printf(s, x1, x2);
+</pre>
+ </blockquote> 
+ In almost all cases, the result will be the same as with this command :
+
+ <blockquote>
+ <pre>
+cout << format(s) % x1 % x2;
+</pre>
+ </blockquote>
+
+ But because some printf format specifications don't translate well into
+ stream formatting options, there are a few notable imperfections in the way
+ Boost.format emulates printf. 
+ In any case, the format class should quietly ignore the unsupported
+ options, so that printf format-strings are always accepted by format and
+ produce almost the same output as printf. 
+ Here is the full list of such differences :
+
+ <ul>
+ <li>'0' and ' ' options : printf ignores these options for
+ non numeric conversions, but format applies them to all types of
+ variables. (so it is possible to use those options on user-defined types,
+ e.g. a Rational class, etc..)</li>
+
+ <li>precision for integral types arguments has a special meaning
+ for printf : 
+ printf( "(%5.3d)" , 7 ) ; prints « ( 007) » 
+ While format, like streams, ignores the precision parameter for integral
+ types conversions.</li>
+
+ <li>the ' printf option (format with thousands grouping
+ characters)) has no effect in format.</li>
+
+ <li>Width or precision set to asterisk (*) are used by printf to
+ read this field from an argument. e.g.
+ printf("%1$d:%2$.*3$d:%4$.*3$d\n", hour, min, precision, sec); 
+ This class does not support this mechanism for now. so such precision or
+ width fields are quietly ignored by the parsing.</li>
+ </ul>Also, note that the special 'n' type-specification (used to
+ tell printf to save in a variable the number of characters output by the
+ formatting) has no effect in format. 
+ Thus format strings containing this type-specification should produce the
+ same converted string by printf or format. It will not cause differences in
+ the formatted strings between printf and format. 
+ To get the number of characters in the formatted string using Boost.Format,
+ you can use the size() member function :
+
+ <blockquote>
+ <pre>
+format formatter("%+5d");
cout << formatter % x;
-unsigned int n = formatter.size();</PRE>
-<HR>
-<H2>User-defined types output</H2>
-All flags which are translated into modification to the stream
-state act recursively within user-defined types. ( the flags remain
-active, and so does the desired format option, for each of the '<<'
-operations that might be called by the user-defined class)
-e.g., with a Rational class, we would have something like :
-
-<PRE STYLE="margin-left: 1cm; margin-right: 1cm">Rational ratio(16,9);
-cerr << format("%#x \n") % ratio; // -> "0x10/0x9 \n"</PRE>
-It's a different story for other formatting options. For example,
-setting width applies to the final output produced by the object, not
-to each of its internal outputs, and that's fortunate :
-<PRE STYLE="margin-left: 1cm; margin-right: 1cm">cerr << format("%-8d") % ratio; // -> "16/9 " and not "16 /9 "
-cerr << format("%=8d") % ratio; // -> " 16/9 " and not " 16 / 9 "</PRE>
- But so does the 0 and ' ' options (contrarily to '+' which is
-directly translated to the stream state by showpos. But no
-such flags exist for the zero and space printf options) and that
-is less natural :
-<PRE STYLE="margin-left: 1cm; margin-right: 1cm">cerr << format("%+08d \n") % ratio; // -> "+00016/9"
-cerr << format("% 08d \n") % ratio; // -> "000 16/9"</PRE>
-It is possible to obtain a better behaviour by carefully designing
-the Rational's operator<< to handle the stream's width,
-alignment and showpos paramaters by itself. This is
-demonstrated in sample_userType.cpp.
-
-<HR>
-<H3>Manipulators, and internal stream state</H3>
-The internal stream state of format is saved before and
-restored after output of an argument; therefore, the modifiers are
-not sticky and affect only the argument they are applied to. The
-default state for streams, as stated by the standard, is : precision
-6, width 0, right alignment, and decimal flag set.
-The state of the internal format stream can be changed by
-manipulators passed along with the argument; via the group
-function, like that :
-<PRE STYLE="margin-left: 1cm; margin-right: 1cm; margin-bottom: 0.5cm">cout << format("%1% %2% %1%\n") % group(hex, showbase, 40) % 50; // prints "0x28 50 0x28\n"</PRE>
- When passing N items inside a 'group' Boost.format needs to
-process manipulators diferently from regular argument, and thus using
-group is subject to the following constraints :
-<OL>
- <LI>the object to be printed must be
- passed as the last item in the group
- 
- <LI>the first N-1 items are treated as manipulators, and if they
- do produce output, it is discarded
- 
-</OL>
-Such manipulators are passed to the streams right before the
-following argument, at every occurence. Note that formatting options
-specified within the format string are overridden by stream state
-modifiers passed this way. For instance in the following code, the
-hex manipulator has priority over the d
-type-specification in the format-string which would set decimal
-output :
-<PRE STYLE="margin-left: 1cm; margin-right: 1cm">cout << format("%1$d %2% %1%\n") % group(hex, showbase, 40) % 50;
-// prints "0x28 50 0x28\n"</PRE><H2>
-Alternatives</H2>
-<UL>
- <LI>printf is the classical
- alternative, that is not type safe and not extendable to
- user-defined types.
- 
- <LI>ofrstream.cc by Karl Nelson's
- design was a big source of inspiration to this format class.
- 
- <LI>James Kanze's library has a format
- class (in srcode/Extended/format ) which looks very well
- polished. Its design has in common with this class the use of
- internal stream for the actual conversions, as well as using
- operators to pass arguments. (but his class, as ofrstream, uses
- operator<< rather than operator% )
- 
- <LI><A HREF="http://groups.yahoo.com/group/boost/files/format3/">Karl
- Nelson's library</A> was intented as demonstration of alternative
- solutions in discussions on Boost's list for the design of
- Boost.format.
- 
-</UL>
-<HR>
-<H2>Exceptions</H2>
-Boost.format enforces a number of rules on the usage of format
-objects. The format-string must obeys the syntax described above, the
-user must supply exactly the right number of arguments before
-outputting to the final destination, and if using modify_item or
-bind_arg, items and arguments index must not be out of range. When
-format detects that one of these rules is not satisfied, it raises a
-corresponding exception, so that the mistakes don't go unnoticed and
-unhandled. But the user can change this behaviour to fit his
-needs, and select which types of errors may raise exceptions using
-the following functions :
-<PRE STYLE="margin-left: 1cm; margin-right: 1cm">
+unsigned int n = formatter.size();
+</pre>
+ </blockquote><a name="user-defined" id="user-defined"></a>
+ <hr>
+
+ <h2>User-defined types output</h2>
+
+ All flags which are translated into modification to the stream state act
+ recursively within user-defined types. ( the flags remain active, and so
+ does the desired format option, for each of the '<<' operations that
+ might be called by the user-defined class)e.g., with a Rational class,
+ we would have something like :
+
+ <blockquote>
+ <pre>
+Rational ratio(16,9);
+cerr << format("%#x \n") % ratio; // -> "0x10/0x9 \n"
+</pre>
+ </blockquote>
+
+ It's a different story for other formatting options. For example,
+ setting width applies to the final output produced by the object, not to
+ each of its internal outputs, and that's fortunate :
+
+ <blockquote>
+ <pre>
+cerr << format("%-8d") % ratio; // -> "16/9 " and not "16 /9 "
+cerr << format("%=8d") % ratio; // -> " 16/9 " and not " 16 / 9 "
+</pre>
+ </blockquote>
+
+ 
+ But so does the 0 and ' ' options (contrarily to '+' which is directly
+ translated to the stream state by showpos. But no such flags exist
+ for the zero and space printf options) 
+ and that is less natural :
+
+ <blockquote>
+ <pre>
+cerr << format("%+08d \n") % ratio; // -> "+00016/9"
+cerr << format("% 08d \n") % ratio; // -> "000 16/9"
+</pre>
+ </blockquote>It is possible to obtain a better behaviour by carefully
+ designing the Rational's operator<< to handle the stream's
+ width, alignment and showpos paramaters by itself. This is
+ demonstrated in <a href=
+ "../example/sample_userType.cpp">sample_userType.cpp</a>. <a name=
+ "manipulators" id="manipulators"></a>
+ <hr>
+
+ <h3>Manipulators, and internal stream state</h3>
+
+ The internal stream state of format is saved before and restored
+ after output of an argument; therefore, the modifiers are not sticky and
+ affect only the argument they are applied to. 
+ The default state for streams, as stated by the standard, is : precision 6,
+ width 0, right alignment, and decimal flag set.
+
+ The state of the internal format stream can be changed by
+ manipulators passed along with the argument; via the group function,
+ like that :
+
+ <blockquote>
+ <pre>
+cout << format("%1% %2% %1%\n") % group(hex, showbase, 40) % 50; // prints "0x28 50 0x28\n"
+</pre>
+ </blockquote>
+
+ 
+ When passing N items inside a 'group' Boost.format needs to process
+ manipulators diferently from regular argument, and thus using group is
+ subject to the following constraints :
+
+ <ol>
+ <li>the object to be printed must be passed as the last item in the
+ group</li>
+
+ <li>the first N-1 items are treated as manipulators, and if they do
+ produce output, it is discarded</li>
+ </ol>
+
+ Such manipulators are passed to the streams right before the following
+ argument, at every occurence. Note that formatting options specified within
+ the format string are overridden by stream state modifiers passed this way.
+ For instance in the following code, the hex manipulator has priority
+ over the d type-specification in the format-string which would set
+ decimal output :
+
+ <blockquote>
+ <pre>
+cout << format("%1$d %2% %1%\n") % group(hex, showbase, 40) % 50;
+// prints "0x28 50 0x28\n"
+</pre>
+ </blockquote><a name="alternatives" id="alternatives"></a>
+
+ <h2>Alternatives</h2>
+
+ <ul>
+ <li>printf is the classical alternative, that is not type safe and
+ not extendable to user-defined types.</li>
+
+ <li>ofrstream.cc by Karl Nelson's design was a big source of inspiration
+ to this format class.</li>
+
+ <li>James Kanze's library has a format class (in
+ srcode/Extended/format ) which looks very well polished. Its
+ design has in common with this class the use of internal stream for the
+ actual conversions, as well as using operators to pass arguments. (but
+ his class, as ofrstream, uses operator<< rather than
+ operator% )</li>
+
+ <li><a href="http://groups.yahoo.com/group/boost/files/format3/">Karl
+ Nelson's library</a> was intented as demonstration of alternative
+ solutions in discussions on Boost's list for the design of
+ Boost.format.</li>
+ </ul><a name="exceptions" id="exceptions"></a>
+ <hr>
+
+ <h2>Exceptions</h2>
+
+ Boost.format enforces a number of rules on the usage of format objects.
+ The format-string must obeys the syntax described above, the user must
+ supply exactly the right number of arguments before outputting to the final
+ destination, and if using modify_item or bind_arg, items and arguments
+ index must not be out of range. 
+ When format detects that one of these rules is not satisfied, it raises a
+ corresponding exception, so that the mistakes don't go unnoticed and
+ unhandled. 
+ But the user can change this behaviour to fit his needs, and select which
+ types of errors may raise exceptions using the following functions :
+
+ <blockquote>
+ <pre>
+
unsigned char exceptions(unsigned char newexcept); // query and set
unsigned char exceptions() const; // just query
-</PRE>
-The user can compute the argument newexcept by combining the
-following atoms using binary arithmetic :
-<UL>
- <LI>boost::io::bad_format_string_bit
- selects errors due to ill-formed format-strings.
- 
- <LI>boost::io::too_few_args_bit
- selects errors due to asking for the srting result before all
- arguments are passed.
- 
- <LI>boost::io::too_many_args_bit
- selects errors due to passing too many arguments.
- 
- <LI>boost::io::out_of_range_bit
- select errors due to out of range index supplied by the user when
- calling modify_item or other functions taking an item index
- (or an argument index)
- 
- <LI>boost::io::all_error_bits
- selects all errors
- 
- <LI>boost::io::no_error_bits selects no error.
- 
-</UL>
-For instance, if you don't want Boost.format to detect bad number
-of arguments, you can define a specific wrapper function for building
-format objects with the right exceptions settings :
-<PRE STYLE="margin-left: 1cm; margin-right: 1cm">
+
+</pre>
+ </blockquote>
+
+ The user can compute the argument newexcept by combining the
+ following atoms using binary arithmetic :
+
+ <ul>
+ <li>boost::io::bad_format_string_bit selects errors due to
+ ill-formed format-strings.</li>
+
+ <li>boost::io::too_few_args_bit selects errors due to asking for
+ the srting result before all arguments are passed.</li>
+
+ <li>boost::io::too_many_args_bit selects errors due to passing too
+ many arguments.</li>
+
+ <li>boost::io::out_of_range_bit select errors due to out of range
+ index supplied by the user when calling modify_item or other
+ functions taking an item index (or an argument index)</li>
+
+ <li>boost::io::all_error_bits selects all errors</li>
+
+ <li>boost::io::no_error_bits selects no error.</li>
+ </ul>
+
+ For instance, if you don't want Boost.format to detect bad number of
+ arguments, you can define a specific wrapper function for building format
+ objects with the right exceptions settings :
+
+ <blockquote>
+ <pre>
+
boost::format my_fmt(const std::string & f_string) {
 using namespace boost::io;
 format fmter(f_string);
 fmter.exceptions( all_error_bits ^ ( too_many_args_bit | too_few_args_bit ) );
 return fmter;
}
-</PRE>
-It is then allowed to give more arguments than needed (they are
-simply ignored) :
-
-<PRE STYLE="margin-left: 1cm; margin-right: 1cm">
-cout << my_fmt(" %1% %2% \n") % 1 % 2 % 3 % 4 % 5;
-</PRE>
-And if we ask for the result before all arguments are supplied, the
-corresponding part of the result is simply empty
-
-<PRE STYLE="margin-left: 1cm; margin-right: 1cm">
-cout << my_fmt(" _%2%_ _%1%_ \n") % 1 ;
-// prints " __ _1_ \n"
-</PRE>
-<HR>
-<H2>A Note about performance</H2>
-The performance of boost::format for formatting a few builtin type
-arguments with reordering can be compared to that of Posix-printf,
-and of the equivalent stream manual operations to give a measure of
-the overhead incurred. The result may greatly depend on the compiler,
-standard library implementation, and the precise choice of
-format-string and arguments.
-Since common stream implementations eventually call functions of
-the printf family for the actual formatting of numbers, in general
-printf will be noticeably faster than the direct stream operations
-And due to to the reordering overhead (allocations to store the
-pieces of string, stream initialisation at each item formatting, ..)
-the direct stream operations would be faster than boost::format, (one
-cas expect a ratio ranging from 2 to 5 or more)
-When iterated formattings are a performance bottleneck,
-performance can be slightly increased by parsing the format string
-into a format object, and copying it at each formatting, in the
-following way.
-<PRE STYLE="margin-left: 1cm; margin-right: 1cm"> const boost::format fmter(fstring);
- dest << boost::format(fmter) % arg1 % arg2 % arg3 ;</PRE>
-As an example of performance results, the author measured the time of
-execution of iterated formattings with 4 different methods
-<OL>
- <LI>posix printf
- 
- <LI>manual stream output (to a dummy
- nullStream stream sending the bytes into oblivion)
- 
- <LI>boost::format copied from a const
- object as shown above
- 
- <LI>the straigt boost::format usage
- 
-</OL>
-the test was compiled with g++-3.3.3 and the following timings
-were measured (in seconds, and ratios) :
-<PRE STYLE="margin-left: 1cm; margin-right: 1cm">string fstring="%3$0#6x %1$20.10E %2$g %3$0+5d \n";
+
+</pre>
+ </blockquote>It is then allowed to give more arguments than needed (they
+ are simply ignored) :
+
+ <blockquote>
+ <pre>
+
+cout << my_fmt(" %1% %2% \n") % 1 % 2 % 3 % 4 % 5;
+
+</pre>
+ </blockquote>And if we ask for the result before all arguments are
+ supplied, the corresponding part of the result is simply empty
+
+ <blockquote>
+ <pre>
+
+cout << my_fmt(" _%2%_ _%1%_ \n") % 1 ;
+// prints " __ _1_ \n"
+
+</pre>
+ </blockquote><a name="performance" id="performance"></a>
+ <hr>
+
+ <h2>A Note about performance</h2>
+
+ The performance of boost::format for formatting a few builtin type
+ arguments with reordering can be compared to that of Posix-printf, and of
+ the equivalent stream manual operations to give a measure of the overhead
+ incurred. The result may greatly depend on the compiler, standard library
+ implementation, and the precise choice of format-string and arguments.
+
+ Since common stream implementations eventually call functions of the
+ printf family for the actual formatting of numbers, in general printf will
+ be noticeably faster than the direct stream operations And due to to the
+ reordering overhead (allocations to store the pieces of string, stream
+ initialisation at each item formatting, ..) the direct stream operations
+ would be faster than boost::format, (one cas expect a ratio ranging from 2
+ to 5 or more)
+
+ When iterated formattings are a performance bottleneck, performance can
+ be slightly increased by parsing the format string into a format object,
+ and copying it at each formatting, in the following way.
+
+ <blockquote>
+ <pre>
+ const boost::format fmter(fstring);
+ dest << boost::format(fmter) % arg1 % arg2 % arg3 ;
+</pre>
+ </blockquote>
+
+ As an example of performance results, the author measured the time of
+ execution of iterated formattings with 4 different methods
+
+ <ol>
+ <li>posix printf</li>
+
+ <li>manual stream output (to a dummy nullStream stream sending the
+ bytes into oblivion)</li>
+
+ <li>boost::format copied from a const object as shown above</li>
+
+ <li>the straigt boost::format usage</li>
+ </ol>
+
+ the test was compiled with g++-3.3.3 and the following timings were
+ measured (in seconds, and ratios) :
+
+ <blockquote>
+ <pre>
+string fstring="%3$0#6x %1$20.10E %2$g %3$0+5d \n";
double arg1=45.23;
double arg2=12.34;
int arg3=23;
@@ -826,10 +916,16 @@
printf : 2.12
nullStream : 3.69, = 1.74057 * printf
boost::format copied :10.02, = 4.72642 * printf , = 2.71545 * nullStream
-boost::format straight :17.03, = 8.03302 * printf , = 4.61518 * nullStream</PRE>
-<HR>
-<H2>Class Interface Extract</H2>
-<PRE STYLE="margin-left: 1cm; margin-right: 1cm">namespace boost {
+boost::format straight :17.03, = 8.03302 * printf , = 4.61518 * nullStream
+</pre>
+ </blockquote><a name="extract" id="extract"></a>
+ <hr>
+
+ <h2>Class Interface Extract</h2>
+
+ <blockquote>
+ <pre>
+namespace boost {

template<class charT, class Traits=std::char_traits<charT> >
class basic_format
@@ -875,52 +971,60 @@
}

-} // namespace boost</PRE>
-<HR>
-<H2>Rationale</H2>
-This class's goal is to bring a better, C++, type-safe and
-type-extendable printf equivalent to be used with streams.
-Precisely, format was designed to provide the following
-features :
-
-<UL>
- <LI>support positional arguments
- (required for internationalisation)
- 
- <LI>accept an unlimited number of
- arguments.
- 
- <LI>make formatting commands visually
- natural.
- 
- <LI>support the use of manipulators to
- modify the display of an argument. in addition to the format-string
- syntax.
- 
- <LI>accept any types of variables, by
- relying on streams for the actual conversion to string. This
- specifically concerns user-defined types, for which the formatting
- options effects should be intuitively natural.
- 
- <LI>provide printf-compatibility, as much as it makes sense in a
- type-safe and type-extendable context.
- 
-</UL>
-In the process of the design, many issues were faced, and some
-choices were made, that might not be intuitively right. But in each
-case they were taken for some reasons.
-<HR>
-<H2>Credits</H2>
-The author of Boost format is Samuel Krempp.   He used ideas
-from Rüdiger Loos' format.hpp and Karl Nelson's formatting
-classes.
-<HR>
-
-Revised
-02 December, 2006
-Copyright © 2002 Samuel Krempp
-Distributed under the Boost Software License, Version 1.0. (See
-accompanying file LICENSE_1_0.txt
-or copy at http://www.boost.org/LICENSE_1_0.txt)
-</BODY>
-</HTML>
\ No newline at end of file
+} // namespace boost
+</pre>
+ </blockquote>
+ <hr>
+ <a name="rationale" id="rationale"></a>
+
+ <h2>Rationale</h2>
+
+ This class's goal is to bring a better, C++, type-safe and
+ type-extendable printf equivalent to be used with
+ streams.Precisely, format was designed to provide the following
+ features :
+
+ <ul>
+ <li>support positional arguments (required for internationalisation)</li>
+
+ <li>accept an unlimited number of arguments.</li>
+
+ <li>make formatting commands visually natural.</li>
+
+ <li>support the use of manipulators to modify the display of an argument.
+ in addition to the format-string syntax.</li>
+
+ <li>accept any types of variables, by relying on streams for the actual
+ conversion to string. This specifically concerns user-defined types, for
+ which the formatting options effects should be intuitively natural.</li>
+
+ <li>provide printf-compatibility, as much as it makes sense in a
+ type-safe and type-extendable context.</li>
+ </ul>
+
+ In the process of the design, many issues were faced, and some choices
+ were made, that might not be intuitively right. But in each case they were
+ taken for some reasons.
+ <hr>
+
+ <h2>Credits</h2>
+
+ The author of Boost format is Samuel Krempp.   He used ideas from
+ Rüdiger Loos' format.hpp and Karl Nelson's formatting classes.
+ <hr>
+
+ <a href="http://validator.w3.org/check?uri=referer"><img border="0" src=
+ "../../../doc/images/valid-html401.png" alt="Valid HTML 4.01 Transitional"
+ height="31" width="88"></a>
+
+ Revised
+ 02 December, 2006
+
+ Copyright © 2002 Samuel Krempp
+
+ Distributed under the Boost Software License, Version 1.0. (See
+ accompanying file LICENSE_1_0.txt or
+ copy at <a href=
+ "http://www.boost.org/LICENSE_1_0.txt">http://www.boost.org/LICENSE_1_0.txt>)
+</body>
+</html>

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