# ExtElement + ExtElement -- addition of Ext-algebra elements

## Synopsis

• Operator: +
• Usage:
u=x + y
• Inputs:
• x, an instance of the type ExtElement, $x$ is of type $E$, where $E$ is of type ExtAlgebra
• y, an instance of the type ExtElement, y is of type E
• Outputs:
• u, an instance of the type ExtElement, $u$ is of type $E$, the sum of $x$ and $y$

## Description

The symbol + is used as infix notation for the Ext-algebra addition. The elements $x$ and $y$ must have the same weight and sign.

 i1 : L = lieAlgebra{a,b,c}/{a b,b c} o1 = L o1 : LieAlgebra i2 : E = extAlgebra(3,L) o2 = E o2 : ExtAlgebra i3 : basis(2,E) o3 = {ext_3, ext_4} o3 : List i4 : ext_4+2 ext_3 o4 = 2ext_3 + ext_4 o4 : E