5.1.11 contract
---------------

Syntax:
contract ( ideal_expression, ideal_expression )
Type:
matrix
Purpose:
contracts each of the n elements of the second ideal J
by each of the m elements of the first ideal I,
producing a m x n matrix.

Contraction is defined on monomials by:


$${\rm contract}(x^A ,  x^B) := \cases{ x^{(B-A)}, &if $B\ge A$
componentwise\cr 0,&otherwise.\cr}$$
where A and B are the multiexponents of the ring variables represented by
$x$.
contract is extended bilinearly to all polynomials.
Example:
  ring r=0,(a,b,c,d),dp;
  ideal I=a2,a2+bc,abc;
  ideal J=a2-bc,abcd;
  print(contract(I,J));
==> 1,0, 
==> 0,ad,
==> 0,d  
See
diff.
<font size="-1">
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; User manual for <a href="http://www.singular.uni-kl.de/"><i>Singular</i></a> version 2-0-4, October 2002,
generated by <a href="http://www.gnu.org/software/texinfo/"><i>texi2html</i></a>.
</font>

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