Explicit functions with discontinous intervals?
I understand that rational functions of certain forms will produce a "hole" or infinitismal break in the graph, like the following:
will obviously appear as the graph of with a hole at . But is there a way to explicitly define a function (supposedly composed of functions which are not defined for all values of x, or that may result in such a function) to explicitly define a function [without using domain restrictions, piecewise representations, or band-aid set theory definitions; (i.e. using set theory to to define the function with the desire discountinuities)] that would naturally have discountinuities over a specific interval? Say I wanted to explicitly define a function that had a complete discontinuity at all values
or more generally
is there a manner in which it is possible to construct a function that would produce this property?
Explicit, non-piece-wise function . No using set theory directly "cut and delete". No given domain restrictions
 is not simply discontinuos at specific values, or holes, of , but rather is discontinuos for
How would one go about creating such a function? Thanks in advance for any advice related to this topic