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7.5.21.0. isInvertibleLeftFraction
Procedure from library olga.lib (see olga_lib).
- Usage:
- isInvertibleLeftFraction(frac, locType, locData), vector frac,
int locType, list/vector/intvec locData
- Purpose:
- check if a fraction is invertible in the specified localization
- Assume:
- Return:
- int
- Note:
- - returns 1, if the numerator of frac is in the denominator set,
- returns 0, otherwise (NOTE: this does NOT mean that the fraction is
not invertible, it just means it could not be determined by the
method above).
Example:
| | LIB "olga.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
poly g1 = x+3;
poly g2 = x*y;
list L = g1,g2;
vector frac = [g1*g2, 17, 0, 0];
isInvertibleLeftFraction(frac, 0, L);
==> 1
ideal p = x-1, y;
frac = [g1, x, 0, 0];
isInvertibleLeftFraction(frac, 1, p);
==> 1
intvec rat = 1,2;
frac = [g1*g2, Dx, 0, 0];
isInvertibleLeftFraction(frac, 2, rat);
==> 0
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