function y = conv(a,b)
#Convolve two vectors.
#y = conv(a,b) returns a vector of length equal to length(a)+length(b)-1.
#If a and b are polynomial coefficient vectors, conv returns the
#coefficients of the product polynomial.
#
#SEE ALSO: deconv, poly, roots, residue, polyval, polyderiv, polyinteg

# Author:
#  Tony Richardson
#  amr@mpl.ucsd.edu
#  June 1994

  if(nargin != 2)
    error("usage: conv(a,b)");
  endif

  if(is_matrix(a) || is_matrix(b))
    error("conv: both arguments must be vectors");
  endif

  la = length(a);
  lb = length(b);

  ly = la + lb - 1;

  # Ensure that both vectors are row vectors.
  if(rows(a) > 1)
    a = reshape(a,1,la);
  endif
  if(rows(b) > 1)
    b = reshape(b,1,lb);
  endif

  # Use the shortest vector as the coefficent vector to filter.
  if (la < lb)
    if(ly>lb)
      x = [b zeros(1,ly-lb)];
    else
      x = b;
    endif
    y = filter(a,1,x);
  else
    if(ly>la)
      x = [a zeros(1,ly-la)];
    else
      x = a;
    endif
    y = filter(b,1,x);
  endif

endfunction