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Boost-Commit : |
Subject: [Boost-commit] svn:boost r83609 - sandbox/precision/libs/precision/doc
From: e_float_at_[hidden]
Date: 2013-03-27 15:34:57
Author: christopher_kormanyos
Date: 2013-03-27 15:34:57 EDT (Wed, 27 Mar 2013)
New Revision: 83609
URL: http://svn.boost.org/trac/boost/changeset/83609
Log:
Tweaks on wording to improve the flow of the document. Proper merging with Paul's typo corrections.
Text files modified:
sandbox/precision/libs/precision/doc/precision.qbk | 66 ++++++++++++++++++++--------------------
1 files changed, 33 insertions(+), 33 deletions(-)
Modified: sandbox/precision/libs/precision/doc/precision.qbk
==============================================================================
--- sandbox/precision/libs/precision/doc/precision.qbk (original)
+++ sandbox/precision/libs/precision/doc/precision.qbk 2013-03-27 15:34:57 EDT (Wed, 27 Mar 2013)
@@ -71,19 +71,13 @@
are to be contained in a new standard library header `<cstdfloat>`.
They will be defined in the `std` namespace.
-It is not proposed to make any changes to `<cmath>`, special functions,
-`<limits>`, or `<complex>`.
-Any of the optional floating-point `typedef`s having specified width
-that are `typedef`ed from the built-in types `float`, `double`, and `long double`
-should automatically be supported by
-the implementation's existing `<cmath>`, special functions,
-`<limits>`, and `<complex>`.
-Support for other `typedef`s is implementation-defined.
-
New C-style macros are proposed to facilitate initialization
of the optional floating-point `typedef`s having specified width
from a floating-point literal constant.
+It is not proposed to make any mandatory changes to `<cmath>`,
+special functions, `<limits>`, or `<complex>`.
+
The main objectives of this proposal are to:
* Extend the benefits of specified-width typedefs for integer types to floating-point types.
@@ -131,7 +125,7 @@
It may also be desirable to extend floating-point precision to
both lower and higher precisions. This can be done by including
-implementation-specific optional floating-point `typedef`s having specified width
+implementation-specific `typedef`s having specified width
that are not derived from `float`, `double`, and `long double`.
Providing optional floating-point `typedef`s having specified width
@@ -237,7 +231,7 @@
Consider an implementation for a supercomputer. This platform might have
`float`, `double`, and `long double` corresponding to IEEE754
`binary32`, `binary64`, and `binary128`, respectively. In addition, this
-platform might have an implementation-specific type with octuple-precision.
+platform might have a floating-point type with octuple-precision.
The implementation for this supercomputer could introduce
its optional floating-point `typedef`s having specified width
into the `std` namespace as shown below.
@@ -246,19 +240,18 @@
namespace std
{
- typedef float float32_t;
- typedef double float64_t;
- typedef long double float128_t;
- typedef my_octuple_precision_type float256_t;
- typedef float256_t floatmax_t;
+ typedef float float32_t;
+ typedef double float64_t;
+ typedef long double float128_t;
+ typedef floating-point type float256_t;
+ typedef float256_t floatmax_t;
}
A cost-sensitive 8-bit microcontroller platform without an FPU
does not have sufficient resources to support the eight-byte, 64-bit
`binary64` type in a feasible fashion.
An implementation for this platform can, however, support
-half-precision `float16_t` using an implementation-specific type
-and single-precision `float32_t`.
+half-precision `float16_t` and single-precision `float32_t`.
This implementation could introduce
its optional floating-point `typedef`s having specified width
into the `std` namespace as shown below.
@@ -267,9 +260,9 @@
namespace std
{
- typedef my_half_precision_type float16_t;
- typedef float float32_t;
- typedef float32_t floatmax_t;
+ typedef floating-point type float16_t;
+ typedef float float32_t;
+ typedef float32_t floatmax_t;
}
The popular [@http://gcc.gnu.org/wiki/x87note Intel X8087 chipset]
@@ -351,6 +344,7 @@
specified width in C++11. A partial synopsis is shown below.
18.4 Integer types [cstdint]
+
18.4.1 Header <cstdint> synopsis [cstdint.syn]
namespace std
@@ -378,7 +372,9 @@
Section 18.4 could be extended as shown below.
18.4? Integer and Floating-Point Types Having Specified Width
+
18.4.1 Header <cstdint> synopsis [cstdint.syn]
+
18.4.2? Header <cstdfloat> synopsis [cstdfloat.syn]
namespace std
@@ -410,7 +406,7 @@
[section:cmathinterop Interoperation with <cmath> and special functions]
-It is not proposed to make any changes to `<cmath>` or special functions.
+It is not proposed to make any mandatory changes to `<cmath>` or special functions.
Any of the optional floating-point `typedef`s having specified width
that are `typedef`ed from the built-in types `float`, `double`, and `long double`
@@ -429,7 +425,7 @@
[section:limitsinterop Interoperation with <limits>]
-It is not proposed to make any changes to `<limits>`.
+It is not proposed to make any mandatory changes to `<limits>`.
Any of the optional floating-point `typedef`s having specified width
that are `typedef`ed from the built-in types `float`, `double`, and `long double`
@@ -449,15 +445,15 @@
[note Each of the optional floating-point `typedef`s having specified width
can only have `true` for the value of `std::numeric_limits<>::is_iec559`
if its underlying type (be it `float`, `double`, `long double` or
-an implementation-dependent type) conforms with its corresponding
-cpecification of `binary16`, `binary32`, `binary64`, or `binary128`
+an implementation-dependent type) conforms with one of
+`binary16`, `binary32`, `binary64`, or `binary128`
in __IEEE_floating_point.]
[endsect] [/section:limitsinterop Interoperation with <limits>]
[section:complexinterop Interoperation with <complex>]
-It is not proposed to make any changes to `<complex>`.
+It is not proposed to make any mandatory changes to `<complex>`.
Any of the optional floating-point `typedef`s having specified width
that are `typedef`ed from the built-in types `float`, `double`, and `long double`
@@ -476,8 +472,10 @@
The proposed `typedef` `float128_t` provides a standardized way
to specify quadruple-precision (__IEEE_Quad) in C++.
-On powerful PCs and workstations, `long double` has been treated
-in a variety of ways, and this has given rise to numerous portability problems.
+On powerful PCs and workstations, implementation-specific versions
+of `long double` as well as various floating-point extensions to 128-bit
+have been treated in a variety of ways.
+This has resulted in numerous portability problems.
The [@http://gcc.gnu.org/wiki/x87note Intel X8087 chipset] is capable of performing
calculations with internal 80-bit registers. This increases the width of the
@@ -506,11 +504,14 @@
at the extremes making implementation of `std::numeric_limits<>::epsilon()` problematic.
It may be useful if future implementations for powerful PCs and workstations
-strive to make `long double` equivalent to quadruple-precision (__IEEE_Quad)
-and to `typedef` this to `float128_t`. Some architectures have hardware support
-for this. Those lacking direct hardware support can use software emulation.
+strive to make implementation-specific extensions to 128-bit floating-point
+or the built-in type `long double` equivalent to `binary128`,
+and to include the corresponding `typedef` to `float128_t`.
-[h4 Survey of existing 128-bit types]
+Some architectures have hardware support for this.
+Those lacking direct hardware support can use software emulation.
+
+[h4 Survey of extended-precision types]
# [@http://gcc.gnu.org/onlinedocs/gcc/Floating-Types.html GNU C supports additional floating types, `__float80` and `__float128` to support 80-bit (XFmode) and 128-bit (TFmode) floating types.]
@@ -558,7 +559,6 @@
[endsect] [/section:context The context among existing implementations]
-
[section:references References]
# [@http://isocpp.org/std/meetings-and-participation/papers-and-mailings isocpp.org C++ papers and mailings]
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