A UGen which determines the index in a buffer at which the value matches a
given input signal. If the input value is not found, it outputs -1.
For example, if the buffer contains values 5, 3, 2, 8, and the input signal is
3, the output will be 1. If the input is 3.001, the output will be -1. Unlike
IndexInBetween , this UGen always searches through the entire buffer until the
value is found or the end has been reached (returning -1).