[Ada] Fix faulty preconditions for trigonometric functions

2018-05-23  Boris Yakobowski  <yakobowski@adacore.com>

gcc/ada/

	* libgnat/a-ngelfu.ads (Arctanh, Arccoth): Fix faulty preconditions.

From-SVN: r260595

gcc/ada/ChangeLog

+2018-05-23  Boris Yakobowski  <yakobowski@adacore.com>
+
+	* libgnat/a-ngelfu.ads (Arctanh, Arccoth): Fix faulty preconditions.
+
 2018-05-23  Arnaud Charlet  <charlet@adacore.com>
 
 	* checks.adb (Minimize_Eliminate_Overflows): Default initialize Lo and

gcc/ada/libgnat/a-ngelfu.ads

@@ -196,10 +196,10 @@ is
        and then (if X = 1.0 then Arccosh'Result = 0.0);
 
    function Arctanh (X : Float_Type'Base) return Float_Type'Base with
-     Pre  => abs X /= 1.0,
+     Pre  => abs X < 1.0,
      Post => (if X = 0.0 then Arctanh'Result = 0.0);
 
    function Arccoth (X : Float_Type'Base) return Float_Type'Base with
-     Pre => X <= 1.0 and abs X /= 1.0;
+     Pre => abs X > 1.0;
 
 end Ada.Numerics.Generic_Elementary_Functions;