draw a rectangle
xrect(x,y,w,h)
xrect(rect) // with rect =[x,y,w,h]
:x,y,w,h four real values defining the rectangle. :
xrect draws a rectangle defined by [x,y,w,h] (upper-left point, width, height) in user coordinates.
WARNING: please note that height is positive downwards.
`plot2d`_(0,0,-1,"010"," ",[-2,-2,2,2])
`xset`_("color",5)
xrect(-1,1,2,2)