|  |  7.3.27 subst (plural) 
See also
 map (plural).Syntax:subst (poly_expression, ring_variable, poly_expression)
 subst (vector _expression, ring_variable, poly_expression)
 subst (ideal_expression, ring_variable, poly_expression)
 subst (module _expression, ring_variable, poly_expression)
Type:poly, vector, ideal or module (corresponding to the first argument)
Purpose: substitutes a ring variable by a polynomial.
Example:|  | LIB "ncalg.lib";
def R = makeUsl2();
// this algebra is U(sl_2)
setring R;
poly C  = e*f*h;
poly C1 = subst(C,e,h^3);
C1;
==> fh4-6fh3+12fh2-8fh
poly C2 = subst(C,f,e+f);
C2;
==> e2h+efh
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