* better check of ArcTan2 bug

tests/webtbs/tbug788.pp

@@ -1,11 +1,68 @@
+{$ifdef FPC}
 Uses Math;
 
+{$else not FPC}
+function degtorad(deg : extended) : extended;
+
+  begin
+     degtorad:=deg*(pi/180.0);
+  end;
+
+function radtodeg(rad : extended) : extended;
+
+  begin
+     radtodeg:=rad*(180.0/pi);
+  end;
+
+ function ArcSin(x : extended) : extended;
+   begin
+     if abs(x)=1.0 then
+       arcsin:=Pi/2
+     else
+       arcsin:=ArcTan(x/sqrt(1-x*x));
+   end;
+ function ArcTan2(x,y : extended) : extended;
+   begin
+     ArcTan2:=ArcTan(x/y);
+   end;
+{$endif not FPC}
+
 Var
    I : Integer;
+   RI,RRI,R0 : extended;
 
 Begin
-   For I := 0 To 359 Do
+   For I := -179 To 179 Do
+   Begin
+      RI:=I;
+      WriteLn( RadToDeg(ArcSin(Sin(DegToRad(RI)))):3:18);
+   End;
+   For I := -89 To 89 Do
    Begin
-      WriteLn( RadToDeg(ArcSin(Sin(DegToRad(Real(I))))):3:18);
-   End
-End.
+      RI:=I;
+      RRI:=RadToDeg(ArcSin( Sin(DegToRad(RI))));
+      WriteLn(RI:3:18,' ',RRI:3:18);
+      If RI<>RRI then
+        begin
+          Writeln('Not exact ',RRI-RI:3:18);
+          if I<>0 then
+            begin
+              Writeln('Percentage error = ',Abs(RRI -RI) *100 / I:3:18);
+              if abs((RRI -RI) *100 / I)>0.0001 then
+                Begin
+                  Writeln('Error too big ');
+                  Halt(1);
+                end;
+            end;
+        end;
+   End;
+   RI:=3;
+   RRI:=1;
+   R0:=1;
+   Writeln(  ArcTan2(ArcTan2(1,1),R0):3:18 , ' should be 0.66577375...');
+   if ArcTan2(ArcTan2(1,1),R0)<>ArcTan(ArcTan(1)/R0) then
+     begin
+       Writeln('There is still a bug in ArcTan2 !');
+       Halt(1);
+     end;
+End.