|  |  D.14.1.17 arrDecone Procedure from libraryarr.lib(see  arr_lib).
 
Example:Usage:
arrDecone(A, k); arrangement A, integer k;
Return:
arr: the deconed hyperplane Arrangement dA
Note:
A has to be non-empty and central. arrDecone is an inverse operation
to arrCone since A == arrDecone(arrCone(A),size(A)+1) for any A.
One can also decone a central arrangement with respect to any hyper-
plane k, but than a coordinate change is necessary to make
H_k = ker(x_k). Since such a coordinate change is not unique,
use arrCoordchange to do so.
 See also:
 arrCone;
 arrDecone;
 arrEssentialize;
 arrIsEssential;
 arrRestrict.|  | LIB "arr.lib";
ring R = 0,(x,y,z),dp;
arr A= ideal(x,y,z,x+y-z);
arrDecone(A,3);
==> _[1]=x
==> _[2]=y
==> _[3]=x+y-1
==> 
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