# Singular

#### D.6.8.4 isEquising

Procedure from library `equising.lib` (see equising_lib).

Usage:
isEquising(F[,m,L]); F poly, m int, L list

Assume:
F defines a deformation of a reduced bivariate polynomial f and the characteristic of the basering does not divide mult(f).
If nv is the number of variables of the basering, then the first nv-2 variables are the deformation parameters.
If the basering is a qring, ideal(basering) must only depend on the deformation parameters.

Compute:
tests if the given family is equisingular along the trivial section.

Return:
int: 1 if the family is equisingular, 0 otherwise.

Note:
L is supposed to be the output of hnexpansion (with the given ordering of the variables appearing in f).
If m is given, the family is considered over A/maxideal(m).
This procedure uses `execute` or calls a procedure using `execute`. printlevel>=2 displays additional information.

Example:
 ```LIB "equising.lib"; ring r = 0,(a,b,x,y),ds; poly F = (x2+2xy+y2+x5)+ay3+bx5; isEquising(F); ==> 0 ideal I = ideal(a); qring q = std(I); poly F = imap(r,F); isEquising(F); ==> 1 ring rr=0,(A,B,C,x,y),ls; poly f=x7+y7+(x-y)^2*x2y2; poly F=f+A*y*diff(f,x)+B*x*diff(f,x); isEquising(F); ==> 0 isEquising(F,2); // computation over Q[a,b] / ^2 ==> 1 ```