# Singular

##### 7.5.22.0. isDenom
Procedure from library `ncloc.lib` (see ncloc_lib).

Usage:
isDenom(p, loc), poly a, ncloc loc

Purpose:
check if p is a valid denominator in the localization loc

Return:
int

Note:
returns 1 or 0, depending whether p is a valid denominator

Example:
 ```LIB "ncloc.lib"; ==> // ** redefining testNcloc (LIB "ncloc.lib";) ring R = 0,(x,y,Dx,Dy),dp; def S = Weyl(); setring S; S; ==> // coefficients: QQ ==> // number of vars : 4 ==> // block 1 : ordering dp ==> // : names x y Dx Dy ==> // block 2 : ordering C ==> // noncommutative relations: ==> // Dxx=x*Dx+1 ==> // Dyy=y*Dy+1 // monoidal localization ncloc loc; poly g1 = x^2*y+x+2; poly g2 = y^3+x*y; list L = g1,g2; loc = L; poly g = g1^2*g2; poly f = g - 1; isDenom(g, loc); ==> 1 isDenom(f, loc); ==> 0 // geometrical localization loc = ideal(x-1,y-3); g = x^2+y-3; f = (x-1)*g; isDenom(g, loc); ==> 1 isDenom(f, loc); ==> 0 // rational localization intvec v = 2; loc = v; g = y^5+17*y^2-4; f = x*y; isDenom(g, loc); ==> 1 isDenom(f, loc); ==> 0 ```