### 1.5 Coordinate system

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))

where `left`

is the smaller x coordinate, `right`

is the
larger x coordinate, and `bottom`

and `top`

are respectively
the smaller and larger y coordinates.