Accurate Evaluation of Polynomials in Legendre Basis

Algorithm 9

Addition of a double-double number and a double number.

function [𝑟ℎ,𝑟𝑙]=𝑎𝑑𝑑_𝑑𝑑_𝑑(𝑎ℎ,𝑎𝑙,𝑏)

[𝑡ℎ,𝑡𝑙]=𝑇𝑤𝑜𝑆𝑢𝑚(𝑎ℎ,𝑏)

𝑡𝑙=𝑎𝑙⊕𝑡𝑙

[𝑟ℎ,𝑟𝑙]=𝐹𝑎𝑠𝑡𝑇𝑤𝑜𝑆𝑢𝑚(𝑡ℎ,𝑡𝑙)