`dp_mod', `dp_rat'
------------------

dp_mod(P,MOD,SUBST)
     :: Converts a disributed polynomial into one with coefficients in
     a finite field.

dp_rat(P)
     :: Converts a distributed polynomial with coefficients in a finite
     field into one with coefficients in the rationals.

RETURN
     distributed polynomial

P
     distributed polynomial

MOD
     prime

SUBST
     list

   * `dp_nf_mod()' and `dp_true_nf_mod()' require distributed
     polynomials with coefficients in a finite field as arguments.
     `dp_mod()' is used to convert distributed polynomials with rational
     number coefficients into appropriate ones.  Polynomials with
     coefficients in a finite field cannot be used as inputs of
     operations with polynomials with rational number coefficients.
     `dp_rat()' is used for such cases.

   * The ground finite field must be set in advance by using `setmod()'.

   * SUBST is such a list as `[[VAR,VALUE],...]'.  This is valid when
     the ground field of the input polynomial is a rational function
     field. VAR's are variables in the ground field and the list means
     that VALUE is substituted for VAR before converting the
     coefficients into elements of a finite field.


References
     *Note `dp_nf dp_nf_mod dp_true_nf dp_true_nf_mod': dp_nf dp_nf_mod
     dp_true_nf dp_true_nf_mod, *Note `subst psubst': subst psubst,
     *Note `setmod': setmod.

