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# coefficientRing -- get the coefficient ring

- Usage:
    `coefficientRing R`
- Inputs:
  - R, a ring
- Outputs:
  - a ring, the coefficient ring of R

## Description

If R is a polynomial ring, then the coefficient ring is the base ring from which the coefficients are drawn. If R is constructed from a polynomial ring as a quotient ring or a fraction ring or a sequence of such operations, then the original coefficient ring is returned.

    i1 : coefficientRing(ZZ/101[a][b])

          ZZ
    o1 = ---[a]
         101

    o1 : PolynomialRing

    i2 : ultimate(coefficientRing,ZZ/101[a][b])

          ZZ
    o2 = ---
         101

    o2 : QuotientRing

## See also

- ultimate -- ultimate value for an iteration
- baseRings -- store the list of base rings of a ring

## Ways to use coefficientRing:

- `coefficientRing(Ring)`

## For the programmer

The object coefficientRing is a method function.

The source of this document is in /build/macaulay2-88fgJW/macaulay2-1.25.11+ds/M2/Macaulay2/packages/Macaulay2Doc/functions/coefficientRing-doc.m2:33:0.