The array to scan.
The evaluation predicate, which should return true if e1 is equal to e2 and false if not. This predicate may be any callable type.
The index of the first match or haystack.length if no match was found.
auto buffer = createBuffer("abcddef"); test!("==")(findAdj(buffer), 3);
test!("==")(findAdj("abcddef"), 3);
Performs a linear scan of haystack from [0 .. haystack.length$(RP), returning the index of the first element that compares equal to the next element in the sequence. Comparisons will be performed using the supplied predicate or '==' if none is supplied.