; docformat = 'rst'
;+
; Takes the dot product of the two input vectors a and b.
; 
; :Examples:
;   product = dotp(vector_a, vector_b)
;-
;+
; :Params:
;   a : in, required, type=vector of int or vector of double
;     Input vector that will be used to calculate the dot product.
;   b : in, required, type=vector of int or vector of double
;     Input vector that will be used to calculate the dot product.
;     
; :Returns:
;   Returns the dot product of the two input vectors.
;-
function dotp,a,b
  if (n_elements(a) eq 0 or n_elements(b) eq 0) then begin
    doc_library, 'dotp'
    return, -1
  endif
  resolve_grid,a,x=ax,y=ay,z=az,w=aw
  resolve_grid,b,x=bx,y=by,z=bz,w=bw
  result=ax*bx
  result+=ay*by
  result+=az*bz
  if n_elements(aw) gt 0 then result+=aw*bw
  return,result
end