needed to compile for users with a non-default value of *read-default-float-format*, as vec2-type is defined as single-float, but users might set *read-default-float-format* might be set to something else (I set to double-float following the recommendation in common lisp recipes)
needed to compile for users with a non-default value of `*read-default-float-format*`, as `vec2-type` is defined as `single-float`, but users might set `*read-default-float-format*` might be set to something else (I set to `double-float` following the recommendation in common lisp recipes)