We can consider geometry and a float value as the inputs, and we want the function to return geometry:
CREATE OR REPLACE FUNCTION chp04.create_grid (geometry, float) RETURNS geometry AS $$
In order to construct the subplots, we will require three lines running parallel to the X axis:
WITH middleline AS ( SELECT ST_MakeLine(ST_Translate($1, -10, 0), ST_Translate($1, 40.0, 0)) AS the_geom ), topline AS ( SELECT ST_MakeLine(ST_Translate($1, -10, 10.0), ST_Translate($1, 40.0, 10)) AS the_geom ), bottomline AS ( SELECT ST_MakeLine(ST_Translate($1, -10, -10.0), ST_Translate($1, 40.0, -10)) AS the_geom ),
And we will require six lines running parallel to the Y axis:
oneline AS ( SELECT ST_MakeLine(ST_Translate($1, -10, 10.0), ...