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7.5.15.0. invertNcfrac
Procedure from library ncfrac.lib (see ncfrac_lib).
- Usage:
- invertNcfrac(frac), ncfrac frac
- Purpose:
- compute the inverse of frac
- Return:
- ncfrac
- Note:
- returns the zero fraction if frac is not invertible
Example:
| | LIB "ncfrac.lib";
==> // ** redefining testNcfrac (LIB "ncfrac.lib";) ./examples/invertNcfrac.s\
ing:1
==> // ** redefining testNcloc ( LIB "ncloc.lib";) ncfrac.lib::mod_init:11\
3
ring R = 0,(x,y,Dx,Dy),dp;
def S = Weyl();
setring S;
ncloc loc = intvec(2);
ncfrac frac1 = list([y,y+1,0,0], loc);
// frac1 is invertible
ncfrac inv = invertNcfrac(frac1);
inv;
==> left repr.: (y+1,y)
==> right repr.: (0,0)
==>
ncfrac frac2 = list([y,x+1,0,0], loc);
// frac2 is not invertible
inv = invertNcfrac(frac2);
inv;
==> left repr.: (1,0)
==> right repr.: (0,1)
==>
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