isolating intervals for real roots of a polynomial
univariate polynomial with integer coefficients
(optional) maximal size of each isolating interval
The command realroot(poly, widthgoal) returns a list of isolating intervals for all real roots of the univariate polynomial poly. The width of the interval is less than or equal to the optional parameter widthgoal, a positive number. If widthgoal is omitted, the most convenient width is used for each interval returned.
Each interval is returned as a list of two rational numbers. The list a,a represents the single point a. The list a,b with a<b represents the open real interval defined by a and b. Multiplicity information is not included. The denominators of a and b are integer powers of 2.
The intervals are sorted in ascending order.
The algorithm behind realroot uses Descartes' rule of signs.
Loos and Collins, Computer Algebra, B. Buchberger, ed.
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