gEDA documents use a coordinate system (internally referred to as `world' coordinates) with coordinates increasing upwards and to the right (i.e. a conventional right-handed Cartesian coordinate system).
Although all coordinates may be positive or negative, gschem only displays objects with positive coordinates (i.e. in the upper right quadrant of the coordinate system). It is therefore recommended to use only positive coordinates.
In the Scheme API, the coordinate of a point is expressed in the format:
(x . y)
and a set of bounds (i.e. a rectangular area in the document plane) is expressed in the format:
((left . top) . (right . bottom))
left is the smaller x coordinate,
right is the
larger x coordinate, and
top are respectively
the smaller and larger y coordinates.