added spreadfun as a local function to tconv - this introduces a code…

… duplication, but the function is really short

gabor/tconv.m

@@ -84,3 +84,27 @@
   h=spreadfun(Th);
 
 end;
+
+function coef=spreadfun(T)
+%SPREADFUN  Spreading function of a matrix
+%   Usage:  c=spreadfun(T);
+%
+%   `spreadfun(T)` computes the spreading function of the operator *T*,
+%   represented as a matrix. The spreading function represent the operator *T*
+%   as a weighted sum of time-frequency shifts. See the help text for
+%   |spreadop| for the exact definition.
+%
+%   See also:  spreadop, tconv, spreadinv, spreadadj
+
+complainif_argnonotinrange(nargin,1,1,mfilename);
+
+if ndims(T)>2 || size(T,1)~=size(T,2)
+    error('Input symbol T must be a square matrix.');
+end;
+
+L=size(T,1);
+
+% The 'full' appearing on the next line is to guard the mex file.
+coef=comp_col2diag(full(T));
+
+coef=fft(coef)/L;