graphene:point-x (p)

p -- a graphene:point-t instance
x -- a number coerced to a single float for the x coordinate

The accessor for the x slot of the graphene:point-t structure gets or sets the x coordinate of the point. The x value is coerced to a single float before assignment.

(graphene:with-point (p 0.5 1.0) (graphene:point-x p))
=> 0.5
(graphene:with-point (p) (setf (graphene:point-x p) 3/2))
=> 1.5