add "make me a circle" thing

genplotting.f90

@@ -107,6 +107,34 @@ subroutine genp_plot_axes(amp)
   call genp_draw( amp, 0.0, 7)
 end subroutine
 ! ---------------------------------------------------------
+subroutine genp_circle(radius, steps, color)
+  real, intent(in)      :: radius
+  integer, intent(in)   :: steps, color
+
+  integer               :: idx
+  real                  :: fk, ang, x, y
+  logical               :: firstdot
+
+  if (steps .LT.3 ) then
+    write(0, '("circle: steps ", I3, " bad value")') steps
+    return
+  endif
+
+  firstdot = .TRUE.
+  do idx=0, steps
+    fk = real(idx) / real(steps)
+    ang = 6.283185307 * fk
+    ! write(0, '(I5, "  ->  ", 2F10.5)') idx, fk, ang
+    x = radius * cos(ang)   ;   y = radius * sin(ang)
+    if (firstdot) then
+      call genp_move(x, y)   ;    firstdot = .FALSE.
+    else
+      call genp_draw(x, y, color)
+    endif
+  enddo
+
+end subroutine
+! ---------------------------------------------------------
 subroutine genp_end (foo)
   integer, intent(in)    :: foo