function DFST = dfsa2dfst_r1(DFSA,c1,c2)
% converts a DFSA to a DFST that replaces 1 char (c1) by another char (c2)
% DFST = dfsa2dfst_r1(DFSA,'@','@') creates the identity map on L(DFSA)

DFST.ALFin = DFSA.ALF;
DFST.ALFou = ['@' DFSA.ALF];
DFST.Q = DFSA.Q;
DFST.q0 = DFSA.q0;
DFST.F = DFSA.F;

DFST = init_dfstd(DFST);
for q=DFSA.Q
  for s=DFSA.ALF
    if (s==c1)
      t = c2;
    else
      t = s;
    end
    p = dfsa_delta(DFSA,q,s);
    DFST = set_dfstd(DFST,q,s,p,t);
  end
end
return