This type represents the Extalgebra of a graded differential Lie algebra $L$, $E=Ext_{UL}(F,F)$, where $F$ is the field of $L$ and $UL$ is the enveloping algebra of $L$. Each object of type ExtAlgebra is itself a type E, and homogeneous elements in E belong also to the type ExtElement, which is the parent of E. The generators of E, see generators(ExtAlgebra), represents a basis for $E$ as a vector space and correspond to the Lie algebra generators for the minimal model $M$ of $L$; however, the homological degree of a generator in $E$ is 1 more than the homological degree for the corresponding generator in $M$ (and also the sign is switched).








The object ExtAlgebra is a type, with ancestor classes MutableHashTable < HashTable < Thing.