anchor.diff:     (casts-to :initform '(v-uvec4 v-vec4 v-dvec4))))
   
   (def-v-type-class v-dvector (v-vector) ())
  -(def-v-type-class v-dvec2 (v-dvector v-td)
  +(def-v-type-class v-dvec2 (v-dvector)
     ((core :initform t :reader core-typep)
      (glsl-string :initform "dvec2" :reader v-glsl-string)
      (element-type :initform 'v-double)
  
positive.code:    (element-type :initform 'v-int)
     (dimensions :initform '(3) :reader v-dimensions)
     (casts-to :initform '(v-uvec3 v-vec3 v-dvec3))))
  (def-v-type-class v-ivec4 (v-ivector v-gvec4)
    ((core :initform t :reader core-typep)
     (glsl-string :initform "ivec4" :reader v-glsl-string)
     (element-type :initform 'v-int)
  
negative.code:    (element-type :initform 'v-float)
     (dimensions :initform '(3) :reader v-dimensions)
     (casts-to :initform '(v-dvec3))))
  (def-v-type-class v-vec4 (v-fvector)
    ((core :initform t :reader core-typep)
     (glsl-string :initform "vec4" :reader v-glsl-string)
     (element-type :initform 'v-float)
     (dimensions :initform '(4) :reader v-dimensions)
     (casts-to :initform '(v-dvec4))))
  
  (def-v-type-class v-bvector (v-vector) ())
  (def-v-type-class v-bvec2 (v-bvector)
    ((core :initform t :reader core-typep)
     (glsl-string :initform "bvec2" :reader v-glsl-string)
  