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GroupLex -- defines a ring where some variables are inverted


MonomialOrder => GroupLex => n inverts the first n variables in the polynomial ring. In the following example, a^-1 is in the ring, but c^-1 is not.
i1 : R = QQ[a..d, MonomialOrder=> GroupLex=>2];
i2 : a^-1

o2 = a

o2 : R
i3 : try c^(-1) else "failed"

o3 = failed


The element a/b is in the fraction ring, while a*b^(-1) belongs to R.

Currently, one cannot compute Gröbner bases in this ring.

For the programmer

The object GroupLex is a symbol.