Hello Benoit,
> I was looking for a portable replacement of `trunc' for systems where
> it is not be available. I saw that gnulib had that (http://
> www.gnu.org/software/gnulib/manual/html_node/trunc.html)
Well, there is a misunderstanding here. That doc says that
1) gnulib has no module supporting this function,
2) all known portability problems are in the "not fixed by gnulib" category.
> invoked path/to/gnulib-tool --import trunc. It did what it was meant
> to do but there was still no trace of `trunc' in my source tree
Now wonder...
But since trunc() is a particularly easy function to implement, I implemented
this now. Also updating the doc.
2007-10-03 Bruno Haible <[EMAIL PROTECTED]>
* modules/trunc: New file.
* lib/trunc.c: New file.
* m4/trunc.m4: New file.
* lib/math.in.h (trunc): New declaration.
* m4/math_h.m4 (gl_MATH_H_DEFAULTS): Initialize GNULIB_TRUNC and
HAVE_DECL_TRUNC.
* modules/math (Makefile.am): Substitute also GNULIB_TRUNC and
HAVE_DECL_TRUNC.
* doc/functions/trunc.texi: Mention the 'trunc' module.
*** modules/trunc.orig 2003-09-23 19:59:22.000000000 +0200
--- modules/trunc 2007-10-04 02:22:04.000000000 +0200
***************
*** 0 ****
--- 1,29 ----
+ Description:
+ trunc() function: round towards zero.
+
+ Files:
+ lib/trunc.c
+ m4/trunc.m4
+
+ Depends-on:
+ math
+ float
+
+ configure.ac:
+ gl_FUNC_TRUNC
+ gl_MATH_MODULE_INDICATOR([trunc])
+
+ Makefile.am:
+
+ Include:
+ <math.h>
+
+ Link:
+ $(TRUNC_LIBM)
+
+ License:
+ LGPL
+
+ Maintainer:
+ Bruno Haible
+
*** lib/trunc.c.orig 2003-09-23 19:59:22.000000000 +0200
--- lib/trunc.c 2007-10-04 02:19:51.000000000 +0200
***************
*** 0 ****
--- 1,68 ----
+ /* Round towards zero.
+ Copyright (C) 2007 Free Software Foundation, Inc.
+
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 2, or (at your option)
+ any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License along
+ with this program; if not, write to the Free Software Foundation,
+ Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
+
+ /* Written by Bruno Haible <[EMAIL PROTECTED]>, 2007. */
+
+ #include <config.h>
+
+ /* Specification. */
+ #include <math.h>
+
+ #include <float.h>
+
+ /* 2^(DBL_MANT_DIG-1). */
+ static const double TWO_MANT_DIG =
+ /* Assume DBL_MANT_DIG <= 4 * 31.
+ Use the identity
+ n = floor(n/4) + floor((n+1)/4) + floor((n+2)/4) + floor((n+3)/4). */
+ (double) (1U << ((DBL_MANT_DIG - 1) / 4))
+ * (double) (1U << ((DBL_MANT_DIG - 1 + 1) / 4))
+ * (double) (1U << ((DBL_MANT_DIG - 1 + 2) / 4))
+ * (double) (1U << ((DBL_MANT_DIG - 1 + 3) / 4));
+
+ double
+ trunc (double x)
+ {
+ /* The use of 'volatile' guarantees that excess precision bits are dropped
+ at each addition step and before the following comparison at the caller's
+ site. It is necessary on x86 systems where double-floats are not IEEE
+ compliant by default, to avoid that the results become platform and
compiler
+ option dependent. 'volatile' is a portable alternative to gcc's
+ -ffloat-store option. */
+ volatile double y = x;
+ volatile double z = y;
+
+ if (z > 0)
+ {
+ /* Round to the next integer (nearest or up or down, doesn't matter).
*/
+ z += TWO_MANT_DIG;
+ z -= TWO_MANT_DIG;
+ /* Enforce rounding down. */
+ if (z > y)
+ z -= 1.0;
+ }
+ else if (z < 0)
+ {
+ /* Round to the next integer (nearest or up or down, doesn't matter).
*/
+ z -= TWO_MANT_DIG;
+ z += TWO_MANT_DIG;
+ /* Enforce rounding up. */
+ if (z < y)
+ z += 1.0;
+ }
+ return z;
+ }
*** m4/trunc.m4.orig 2003-09-23 19:59:22.000000000 +0200
--- m4/trunc.m4 2007-10-04 02:41:25.000000000 +0200
***************
*** 0 ****
--- 1,46 ----
+ # trunc.m4 serial 1
+ dnl Copyright (C) 2007 Free Software Foundation, Inc.
+ dnl This file is free software; the Free Software Foundation
+ dnl gives unlimited permission to copy and/or distribute it,
+ dnl with or without modifications, as long as this notice is preserved.
+
+ AC_DEFUN([gl_FUNC_TRUNC],
+ [
+ AC_REQUIRE([gl_MATH_H_DEFAULTS])
+ dnl Test whether trunc() is declared.
+ AC_CHECK_DECLS([trunc], , , [#include <math.h>])
+ if test "$ac_cv_have_decl_trunc" = yes; then
+ dnl Test whether trunc() can be used without libm.
+ TRUNC_LIBM=?
+ AC_TRY_LINK([
+ #ifndef __NO_MATH_INLINES
+ # define __NO_MATH_INLINES 1 /* for glibc */
+ #endif
+ #include <math.h>
+ double x;],
+ [x = trunc(x);],
+ [TRUNC_LIBM=])
+ if test "$TRUNC_LIBM" = "?"; then
+ save_LIBS="$LIBS"
+ LIBS="$LIBS -lm"
+ AC_TRY_LINK([
+ #ifndef __NO_MATH_INLINES
+ # define __NO_MATH_INLINES 1 /* for glibc */
+ #endif
+ #include <math.h>
+ double x;],
+ [x = trunc(x);],
+ [TRUNC_LIBM="-lm"])
+ LIBS="$save_LIBS"
+ fi
+ if test "$TRUNC_LIBM" = "?"; then
+ TRUNC_LIBM=
+ fi
+ else
+ HAVE_DECL_TRUNC=0
+ AC_LIBOBJ([trunc])
+ TRUNC_LIBM=
+ fi
+ AC_SUBST([HAVE_DECL_TRUNC])
+ AC_SUBST([TRUNC_LIBM])
+ ])
*** lib/math.in.h.orig 2007-10-04 03:07:40.000000000 +0200
--- lib/math.in.h 2007-10-04 02:00:57.000000000 +0200
***************
*** 211,216 ****
--- 211,229 ----
tanl (x))
#endif
+ #if @GNULIB_TRUNC@
+ # if [EMAIL PROTECTED]@
+ # define trunc rpl_trunc
+ extern double trunc (double x);
+ # endif
+ #elif defined GNULIB_POSIXCHECK
+ # undef trunc
+ # define trunc(x) \
+ (GL_LINK_WARNING ("trunc is unportable - " \
+ "use gnulib module trunc for portability"), \
+ trunc (x))
+ #endif
+
#if @GNULIB_SIGNBIT@
# if @REPLACE_SIGNBIT@
*** m4/math_h.m4.orig 2007-10-04 03:07:40.000000000 +0200
--- m4/math_h.m4 2007-10-04 01:58:05.000000000 +0200
***************
*** 1,4 ****
! # math_h.m4 serial 5
dnl Copyright (C) 2007 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
--- 1,4 ----
! # math_h.m4 serial 6
dnl Copyright (C) 2007 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
***************
*** 24,29 ****
--- 24,30 ----
GNULIB_LDEXPL=0; AC_SUBST([GNULIB_LDEXPL])
GNULIB_MATHL=0; AC_SUBST([GNULIB_MATHL])
GNULIB_SIGNBIT=0; AC_SUBST([GNULIB_SIGNBIT])
+ GNULIB_TRUNC=0; AC_SUBST([GNULIB_TRUNC])
dnl Assume proper GNU behavior unless another module says otherwise.
HAVE_DECL_ACOSL=1; AC_SUBST([HAVE_DECL_ACOSL])
HAVE_DECL_ASINL=1; AC_SUBST([HAVE_DECL_ASINL])
***************
*** 38,43 ****
--- 39,45 ----
HAVE_DECL_SINL=1; AC_SUBST([HAVE_DECL_SINL])
HAVE_DECL_SQRTL=1; AC_SUBST([HAVE_DECL_SQRTL])
HAVE_DECL_TANL=1; AC_SUBST([HAVE_DECL_TANL])
+ HAVE_DECL_TRUNC=1; AC_SUBST([HAVE_DECL_TRUNC])
REPLACE_FREXP=0; AC_SUBST([REPLACE_FREXP])
REPLACE_FREXPL=0; AC_SUBST([REPLACE_FREXPL])
REPLACE_LDEXPL=0; AC_SUBST([REPLACE_LDEXPL])
*** modules/math.orig 2007-10-04 03:07:40.000000000 +0200
--- modules/math 2007-10-04 02:02:34.000000000 +0200
***************
*** 27,32 ****
--- 27,33 ----
-e 's|@''GNULIB_LDEXPL''@|$(GNULIB_LDEXPL)|g' \
-e 's|@''GNULIB_MATHL''@|$(GNULIB_MATHL)|g' \
-e 's|@''GNULIB_SIGNBIT''@|$(GNULIB_SIGNBIT)|g' \
+ -e 's|@''GNULIB_TRUNC''@|$(GNULIB_TRUNC)|g' \
-e 's|@''HAVE_DECL_ACOSL''@|$(HAVE_DECL_ACOSL)|g' \
-e 's|@''HAVE_DECL_ASINL''@|$(HAVE_DECL_ASINL)|g' \
-e 's|@''HAVE_DECL_ATANL''@|$(HAVE_DECL_ATANL)|g' \
***************
*** 40,45 ****
--- 41,47 ----
-e 's|@''HAVE_DECL_SINL''@|$(HAVE_DECL_SINL)|g' \
-e 's|@''HAVE_DECL_SQRTL''@|$(HAVE_DECL_SQRTL)|g' \
-e 's|@''HAVE_DECL_TANL''@|$(HAVE_DECL_TANL)|g' \
+ -e 's|@''HAVE_DECL_TRUNC''@|$(HAVE_DECL_TRUNC)|g' \
-e 's|@''REPLACE_FREXP''@|$(REPLACE_FREXP)|g' \
-e 's|@''REPLACE_FREXPL''@|$(REPLACE_FREXPL)|g' \
-e 's|@''REPLACE_LDEXPL''@|$(REPLACE_LDEXPL)|g' \
*** doc/functions/trunc.texi.orig 2007-10-04 03:07:40.000000000 +0200
--- doc/functions/trunc.texi 2007-10-04 02:42:37.000000000 +0200
***************
*** 4,18 ****
POSIX specification: @url{http://www.opengroup.org/susv3xsh/trunc.html}
! Gnulib module: ---
Portability problems fixed by Gnulib:
@itemize
@end itemize
Portability problems not fixed by Gnulib:
@itemize
- @item
- This function is missing on some platforms:
- FreeBSD 5.2.1, NetBSD 3.0, OpenBSD 3.8, Solaris 9, Interix 3.5.
@end itemize
--- 4,18 ----
POSIX specification: @url{http://www.opengroup.org/susv3xsh/trunc.html}
! Gnulib module: trunc
Portability problems fixed by Gnulib:
@itemize
+ @item
+ This function is missing on some platforms:
+ FreeBSD 5.2.1, NetBSD 3.0, OpenBSD 3.8, Solaris 9, Interix 3.5.
@end itemize
Portability problems not fixed by Gnulib:
@itemize
@end itemize
