  We develop several applications of the fact that the Yokonuma--Hecke algebra
of the general linear group GL is isomorphic to a direct sum of matrix algebras
associated to Iwahori--Hecke algebras of type A. This includes a description of
the semisimple and modular representation theory of the Yokonuma--Hecke
algebras of GL and a complete classification of all the Markov traces for them.
Finally, from these Markov traces, we construct 3-variables polynomials which
are invariants for framed and classical knots and links, and investigate their
properties with the help of the isomorphism.
