View source for CoCoA:Subst

  <command>
    <title>Subst</title>
    <short_description>substitute values for indeterminates</short_description>

    <description>
The first form of this function substitutes <tt>F_i</tt> for <tt>X_i</tt> in the
expression E.  The second form is a shorthand for the first in the
case of a single indeterminate.  When substituting for the
indeterminates in order, it is easier to use <ttref>Eval</ttref>.

<example>
  Use R ::= Q[x,y,z,t];
  F := x+y+z+t^2;
  Subst(F,x,-2);
t^2 + y + z - 2
-------------------------------
  Subst(F,x,z/y);
(yt^2 + y^2 + yz + z)/y
-------------------------------
  Subst(F,[[x,x^2],[y,y^3],[z,t^5]]);
t^5 + y^3 + x^2 + t^2
-------------------------------
  Eval(F,[x^2,y^3,t^5]); -- the same thing as above
t^5 + y^3 + x^2 + t^2
-------------------------------
  MySubst := [[y,1],[t,3z-x]];
  Subst(xyzt,MySubst);  -- substitute into the function xyzt
-x^2z + 3xz^2
-------------------------------
</example>
    </description>

    <syntax>
Subst(E:OBJECT,X,F):OBJECT
Subst(E:OBJECT,[[X_1,F_1],...,[X_r,F_r]]):OBJECT

where each X or X_i is an indeterminate and each F or F_i is a number,
polynomial, or rational function.
</syntax>

    <see>Eval</see>
    <see>Evaluation of Polynomials</see>
    <see>Image</see>
    <see>QZP</see>
    <see>ZPQ</see>
    <see>Substitutions</see>

    <type>polynomial</type>
    <type>ratfun</type>

    <key>subst</key>
  </command>