# Pullback -- pullback in the category of rings

## Description

Pullback is a package that implements pullback for diagrams of rings

## Caveat

Works only for maps of rings finitely generated over a base field and one of the two maps is surjective

## Authors

• Drew Ellingson
• Karl Schwede

## Version

This documentation describes version 1.03 of Pullback.

## Source code

The source code from which this documentation is derived is in the file Pullback.m2.

## Exports

• Functions and commands
• Methods
• "internalUseDirectSum(Ring,Ring)" -- see internalUseDirectSum -- Compute direct sum of two rings.
• "pullback(RingMap,RingMap)" -- see pullback -- Compute the pullback of a diagram of rings

## For the programmer

The object Pullback is .