--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,14 @@
+2011-10-10  Bruno Haible  <bruno@clisp.org>
+
+	tanl: Simplify for platforms where 'long double' == 'double'.
+	* lib/tanl.c (tanl) [HAVE_SAME_LONG_DOUBLE_AS_DOUBLE]: New alternative
+	implementation.
+	* m4/tanl.m4 (gl_FUNC_TANL): Require gl_LONG_DOUBLE_VS_DOUBLE.
+	Determine TANL_LIBM according to HAVE_SAME_LONG_DOUBLE_AS_DOUBLE.
+	* modules/tanl (Depends-on): Add tan. Update conditions.
+	(configure.ac): Don't compile trigl.c if
+	HAVE_SAME_LONG_DOUBLE_AS_DOUBLE.
+
 2011-10-10  Bruno Haible  <bruno@clisp.org>
 
 	cosl: Simplify for platforms where 'long double' == 'double'.

--- a/lib/tanl.c
+++ b/lib/tanl.c
@@ -19,6 +19,16 @@
 /* Specification.  */
 #include <math.h>
 
+#if HAVE_SAME_LONG_DOUBLE_AS_DOUBLE
+
+long double
+tanl (long double x)
+{
+  return tan (x);
+}
+
+#else
+
 /* tanl(x)
  * Return tangent function of x.
  *
@@ -49,7 +59,7 @@
  *      TRIG(x) returns trig(x) nearly rounded
  */
 
-#include "trigl.h"
+# include "trigl.h"
 
 /*
  * ====================================================
@@ -208,6 +218,8 @@
     }
 }
 
+#endif
+
 #if 0
 int
 main (void)

--- a/m4/tanl.m4
+++ b/m4/tanl.m4
@@ -1,4 +1,4 @@
-# tanl.m4 serial 5
+# tanl.m4 serial 6
 dnl Copyright (C) 2010-2011 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -7,6 +7,8 @@
 AC_DEFUN([gl_FUNC_TANL],
 [
   AC_REQUIRE([gl_MATH_H_DEFAULTS])
+  AC_REQUIRE([gl_LONG_DOUBLE_VS_DOUBLE])
+
   dnl Persuade glibc <math.h> to declare tanl().
   AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
 
@@ -56,24 +58,29 @@
     HAVE_DECL_TANL=0
     HAVE_TANL=0
     dnl Find libraries needed to link lib/tanl.c, lib/trigl.c.
-    AC_REQUIRE([gl_FUNC_ISNANL])
-    AC_REQUIRE([gl_FUNC_FLOOR])
-    AC_REQUIRE([gl_FUNC_FLOORL])
-    dnl Append $ISNANL_LIBM to TANL_LIBM, avoiding gratuitous duplicates.
-    case " $TANL_LIBM " in
-      *" $ISNANL_LIBM "*) ;;
-      *) TANL_LIBM="$TANL_LIBM $ISNANL_LIBM" ;;
-    esac
-    dnl Append $FLOOR_LIBM to TANL_LIBM, avoiding gratuitous duplicates.
-    case " $TANL_LIBM " in
-      *" $FLOOR_LIBM "*) ;;
-      *) TANL_LIBM="$TANL_LIBM $FLOOR_LIBM" ;;
-    esac
-    dnl Append $FLOORL_LIBM to TANL_LIBM, avoiding gratuitous duplicates.
-    case " $TANL_LIBM " in
-      *" $FLOORL_LIBM "*) ;;
-      *) TANL_LIBM="$TANL_LIBM $FLOORL_LIBM" ;;
-    esac
+    if test $HAVE_SAME_LONG_DOUBLE_AS_DOUBLE = 1; then
+      AC_REQUIRE([gl_FUNC_TAN])
+      TANL_LIBM="$TAN_LIBM"
+    else
+      AC_REQUIRE([gl_FUNC_ISNANL])
+      AC_REQUIRE([gl_FUNC_FLOOR])
+      AC_REQUIRE([gl_FUNC_FLOORL])
+      dnl Append $ISNANL_LIBM to TANL_LIBM, avoiding gratuitous duplicates.
+      case " $TANL_LIBM " in
+        *" $ISNANL_LIBM "*) ;;
+        *) TANL_LIBM="$TANL_LIBM $ISNANL_LIBM" ;;
+      esac
+      dnl Append $FLOOR_LIBM to TANL_LIBM, avoiding gratuitous duplicates.
+      case " $TANL_LIBM " in
+        *" $FLOOR_LIBM "*) ;;
+        *) TANL_LIBM="$TANL_LIBM $FLOOR_LIBM" ;;
+      esac
+      dnl Append $FLOORL_LIBM to TANL_LIBM, avoiding gratuitous duplicates.
+      case " $TANL_LIBM " in
+        *" $FLOORL_LIBM "*) ;;
+        *) TANL_LIBM="$TANL_LIBM $FLOORL_LIBM" ;;
+      esac
+    fi
   fi
   AC_SUBST([TANL_LIBM])
 ])

--- a/modules/tanl
+++ b/modules/tanl
@@ -10,16 +10,19 @@
 Depends-on:
 math
 extensions
-float           [test $HAVE_TANL = 0]
-isnanl          [test $HAVE_TANL = 0]
-floor           [test $HAVE_TANL = 0]
-floorl          [test $HAVE_TANL = 0]
+tan             [test $HAVE_TANL = 0 && test $HAVE_SAME_LONG_DOUBLE_AS_DOUBLE = 1]
+float           [test $HAVE_TANL = 0 && test $HAVE_SAME_LONG_DOUBLE_AS_DOUBLE = 0]
+isnanl          [test $HAVE_TANL = 0 && test $HAVE_SAME_LONG_DOUBLE_AS_DOUBLE = 0]
+floor           [test $HAVE_TANL = 0 && test $HAVE_SAME_LONG_DOUBLE_AS_DOUBLE = 0]
+floorl          [test $HAVE_TANL = 0 && test $HAVE_SAME_LONG_DOUBLE_AS_DOUBLE = 0]
 
 configure.ac:
 gl_FUNC_TANL
 if test $HAVE_TANL = 0; then
   AC_LIBOBJ([tanl])
-  AC_LIBOBJ([trigl])
+  if test $HAVE_SAME_LONG_DOUBLE_AS_DOUBLE = 0; then
+    AC_LIBOBJ([trigl])
+  fi
 fi
 gl_MATH_MODULE_INDICATOR([tanl])