Description:

• tripledouble is both a function and a constant.
• As a function, it rounds its argument to the nearest number that can be written as the sum of three double precision numbers.
• The algorithm used to compute tripledouble(x) is the following: let xh = double(x), let xm = double(x - xh) and let xl = double(x - xh - xm). Return the number xh + xm + xl. Note that if the current precision is not sufficient to represent exactly xh + xm + xl, a rounding will occur and the result of tripledouble(x) will be useless.
• As a constant, it symbolizes the triple-double precision format. It is used in contexts when a precision format is necessary, e.g. in the commands roundcoefficients and implementpoly. See the corresponding help pages for examples.