# Singular

#### D.4.4.5 isCI

Procedure from library `cisimplicial.lib` (see cisimplicial_lib).

Usage:
isCI(A); A is an integral matrix

Return:
1 if the simplicial toric ideal I(A) is a complete intersection and 0 otherwise. If printlevel > 0 and I(A) is a complete intersection it also shows a minimal set of generators of I(A)

Assume:
A is an m x n integral matrix with nonnegative entries and for every 1 <= i <= m, there exist a column in A whose i-th coordinate is not null and the rest are 0.

Example:
 ```LIB "cisimplicial.lib"; intmat A[2][5] = 60,0,140,150,21,0,60,140,150,21; print(A); ==> 60 0 140 150 21 ==> 0 60 140 150 21 printlevel = 0; isCI(A); ==> // It is a complete intersection ==> 1 printlevel = 1; isCI(A); ==> // Generators of the toric ideal ==> toric[1]=-x(1)^7*x(2)^7+x(3)^3 ==> toric[2]=x(5)^10-x(1)*x(2)*x(4) ==> toric[3]=-x(1)^5*x(2)^5+x(4)^2 ==> // It is a complete intersection ==> 1 intmat B[3][5] = 12,0,0,1,2,0,10,0,3,2,0,0,8,3,3; print(B); ==> 12 0 0 1 2 ==> 0 10 0 3 2 ==> 0 0 8 3 3 isCI(B); ==> // It is NOT a Complete Intersection. ==> 0 printlevel=0; ```