--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,16 @@
 2011-10-08  Bruno Haible  <bruno@clisp.org>
 
+	New module 'atanf'.
+	* lib/math.in.h (atanf): New declaration.
+	* lib/atanf.c: New file.
+	* m4/atanf.m4: New file.
+	* m4/math_h.m4 (gl_MATH_H): Test whether atanf is declared.
+	(gl_MATH_H_DEFAULTS): Initialize GNULIB_ATANF, HAVE_ATANF.
+	* modules/math (Makefile.am): Substitute GNULIB_ATANF, HAVE_ATANF.
+	* modules/atanf: New file.
+	* tests/test-math-c++.cc: Check the declaration of atanf.
+	* doc/posix-functions/atanf.texi: Mention the new module.
+
 	atan: Use a .m4 file.
 	* m4/atan.m4: New file.
 	* modules/atan (Files): Add it.

--- a/doc/posix-functions/atanf.texi
+++ b/doc/posix-functions/atanf.texi
@@ -4,14 +4,10 @@
 
 POSIX specification:@* @url{http://www.opengroup.org/onlinepubs/9699919799/functions/atanf.html}
 
-Gnulib module: ---
+Gnulib module: atanf
 
 Portability problems fixed by Gnulib:
 @itemize
-@end itemize
-
-Portability problems not fixed by Gnulib:
-@itemize
 @item
 This function is missing on some platforms:
 Minix 3.1.8, AIX 5.1, Solaris 9.
@@ -19,3 +15,7 @@
 This function is only defined as a macro with arguments on some platforms:
 MSVC 9.
 @end itemize
+
+Portability problems not fixed by Gnulib:
+@itemize
+@end itemize

new file mode 100644
--- /dev/null
+++ b/lib/atanf.c
@@ -0,0 +1,26 @@
+/* Inverse tangent function.
+   Copyright (C) 2011 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 3 of the License, 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, see <http://www.gnu.org/licenses/>.  */
+
+#include <config.h>
+
+/* Specification.  */
+#include <math.h>
+
+float
+atanf (float x)
+{
+  return (float) atan ((double) x);
+}

--- a/lib/math.in.h
+++ b/lib/math.in.h
@@ -168,6 +168,21 @@
 #endif
 
 
+#if @GNULIB_ATANF@
+# if !@HAVE_ATANF@
+#  undef atanf
+_GL_FUNCDECL_SYS (atanf, float, (float x));
+# endif
+_GL_CXXALIAS_SYS (atanf, float, (float x));
+_GL_CXXALIASWARN (atanf);
+#elif defined GNULIB_POSIXCHECK
+# undef atanf
+# if HAVE_RAW_DECL_ATANF
+_GL_WARN_ON_USE (atanf, "atanf is unportable - "
+                 "use gnulib module atanf for portability");
+# endif
+#endif
+
 #if @GNULIB_ATANL@
 # if !@HAVE_ATANL@ || !@HAVE_DECL_ATANL@
 _GL_FUNCDECL_SYS (atanl, long double, (long double x));

new file mode 100644
--- /dev/null
+++ b/m4/atanf.m4
@@ -0,0 +1,25 @@
+# atanf.m4 serial 1
+dnl Copyright (C) 2011 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_ATANF],
+[
+  AC_REQUIRE([gl_MATH_H_DEFAULTS])
+  AC_REQUIRE([gl_FUNC_ATAN])
+
+  dnl Test whether atanf() exists. Assume that atanf(), if it exists, is
+  dnl defined in the same library as atan().
+  save_LIBS="$LIBS"
+  LIBS="$LIBS $ATAN_LIBM"
+  AC_CHECK_FUNCS([atanf])
+  LIBS="$save_LIBS"
+  if test $ac_cv_func_atanf = yes; then
+    ATANF_LIBM="$ATAN_LIBM"
+  else
+    HAVE_ATANF=0
+    ATANF_LIBM="$ATAN_LIBM"
+  fi
+  AC_SUBST([ATANF_LIBM])
+])

--- a/m4/math_h.m4
+++ b/m4/math_h.m4
@@ -1,4 +1,4 @@
-# math_h.m4 serial 41
+# math_h.m4 serial 42
 dnl Copyright (C) 2007-2011 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -39,7 +39,7 @@
   dnl Check for declarations of anything we want to poison if the
   dnl corresponding gnulib module is not in use.
   gl_WARN_ON_USE_PREPARE([[#include <math.h>]],
-    [acosf acosl asinf asinl atanl ceilf ceill cosf cosl
+    [acosf acosl asinf asinl atanf atanl ceilf ceill cosf cosl
      expf expl fabsf floorf floorl fmodf frexpf frexpl
      ldexpf ldexpl logb logf logl log10f modff powf
      round roundf roundl sinf sinl sqrtf sqrtl
@@ -61,6 +61,7 @@
   GNULIB_ACOSL=0;    AC_SUBST([GNULIB_ACOSL])
   GNULIB_ASINF=0;    AC_SUBST([GNULIB_ASINF])
   GNULIB_ASINL=0;    AC_SUBST([GNULIB_ASINL])
+  GNULIB_ATANF=0;    AC_SUBST([GNULIB_ATANF])
   GNULIB_ATANL=0;    AC_SUBST([GNULIB_ATANL])
   GNULIB_CEIL=0;     AC_SUBST([GNULIB_CEIL])
   GNULIB_CEILF=0;    AC_SUBST([GNULIB_CEILF])
@@ -109,6 +110,7 @@
   HAVE_ACOSL=1;                AC_SUBST([HAVE_ACOSL])
   HAVE_ASINF=1;                AC_SUBST([HAVE_ASINF])
   HAVE_ASINL=1;                AC_SUBST([HAVE_ASINL])
+  HAVE_ATANF=1;                AC_SUBST([HAVE_ATANF])
   HAVE_ATANL=1;                AC_SUBST([HAVE_ATANL])
   HAVE_COSF=1;                 AC_SUBST([HAVE_COSF])
   HAVE_COSL=1;                 AC_SUBST([HAVE_COSL])

new file mode 100644
--- /dev/null
+++ b/modules/atanf
@@ -0,0 +1,31 @@
+Description:
+atanf() function: inverse tangent function.
+
+Files:
+lib/atanf.c
+m4/atanf.m4
+
+Depends-on:
+math
+atan            [test $HAVE_ATANF = 0]
+
+configure.ac:
+gl_FUNC_ATANF
+if test $HAVE_ATANF = 0; then
+  AC_LIBOBJ([atanf])
+fi
+gl_MATH_MODULE_INDICATOR([atanf])
+
+Makefile.am:
+
+Include:
+<math.h>
+
+Link:
+$(ATANF_LIBM)
+
+License:
+LGPL
+
+Maintainer:
+Bruno Haible

--- a/modules/math
+++ b/modules/math
@@ -32,6 +32,7 @@
 	      -e 's/@''GNULIB_ACOSL''@/$(GNULIB_ACOSL)/g' \
 	      -e 's/@''GNULIB_ASINF''@/$(GNULIB_ASINF)/g' \
 	      -e 's/@''GNULIB_ASINL''@/$(GNULIB_ASINL)/g' \
+	      -e 's/@''GNULIB_ATANF''@/$(GNULIB_ATANF)/g' \
 	      -e 's/@''GNULIB_ATANL''@/$(GNULIB_ATANL)/g' \
 	      -e 's/@''GNULIB_CEIL''@/$(GNULIB_CEIL)/g' \
 	      -e 's/@''GNULIB_CEILF''@/$(GNULIB_CEILF)/g' \
@@ -80,6 +81,7 @@
 	      -e 's|@''HAVE_ACOSL''@|$(HAVE_ACOSL)|g' \
 	      -e 's|@''HAVE_ASINF''@|$(HAVE_ASINF)|g' \
 	      -e 's|@''HAVE_ASINL''@|$(HAVE_ASINL)|g' \
+	      -e 's|@''HAVE_ATANF''@|$(HAVE_ATANF)|g' \
 	      -e 's|@''HAVE_ATANL''@|$(HAVE_ATANL)|g' \
 	      -e 's|@''HAVE_COSF''@|$(HAVE_COSF)|g' \
 	      -e 's|@''HAVE_COSL''@|$(HAVE_COSL)|g' \

--- a/tests/test-math-c++.cc
+++ b/tests/test-math-c++.cc
@@ -32,6 +32,9 @@
 SIGNATURE_CHECK (GNULIB_NAMESPACE::asinf, float, (float));
 #endif
 //SIGNATURE_CHECK (GNULIB_NAMESPACE::asin, double, (double));
+#if GNULIB_TEST_ATANF
+SIGNATURE_CHECK (GNULIB_NAMESPACE::atanf, float, (float));
+#endif
 //SIGNATURE_CHECK (GNULIB_NAMESPACE::atan, double, (double));
 //SIGNATURE_CHECK (GNULIB_NAMESPACE::atan2, double, (double, double));
 //SIGNATURE_CHECK (GNULIB_NAMESPACE::cbrt, double, (double));