; UVBXFN
;---------------------------------------------------------------
;! type of function used when counting for uniform weighting
;# ADVERB UV IMAGING
;-----------------------------------------------------------------------
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;-----------------------------------------------------------------------
;---------------------------------------------------------------
UVBXFN     LLLLLLLLLLLLUUUUUUUUUUUU CCCCCCCCCCCCCCCCCCCCCCCCCCCCC
----------------------------------------------------------------
UVBXFN
Type: Adverb   (Real)
Use: The type of function used  when counting for uniform
     weighting.  If UVBOX = 0, this is irrelevant since all
     functions are 1 at the center cell.  If UVBXFN < 0, the
     function is taken as a function in U and V [i.e. the
     counting weight = f(du)*f(dv)]; if UVBXFN > 0, the function
     is taken as a function in radius [i.e. the counting weight
     = f(sqrt(du*du+dv*dv))] giving everything approxiamtely
     circular support.

     If ABS(UVBXFN) = K, then

        K = 1 : Pill box      f(x) = 1             (x <= UVBOX)

        K = 2 : linear        f(x) = 1 - x / (UVBOX+1)

        K = 3 : exponential   f(x) = exp(-2x/(UVBOX+1))

        K = 4 : Gaussian      f(x) = exp(-(2x/(UVBOX+1))**2)

        Other details: f(x) >= 0 and f(x) = 0 when x > UVBOX.
        du and dv take only integer values: 0, 1, 2, ... UVBOX.
Null value:   0 => 1, < -4 => -1, > 4 => 1
Tasks:
  IMAGR.....Fourier transform and Clean UV data with a full range of
            calibration (application), weighting, Cleaning, and
            wide-field correction options.
  SCIMG.....Full-featured imaging plus self-calibration loop with
            editing.
  SCMAP.....Imaging plus self-calibration loop with editing.
Procedures:
  LINIMAGE..Build image cube from multi-IF data set.
----------------------------------------------------------------
