Substitute in parallel all elements in r which equal (according to pred) ss[2*n] with ss[2*n + 1] for n = 0, 1, 2, ....
Substitute in parallel all subsequences in r which equal (according to pred) ss[2*n] with ss[2*n + 1] for n = 0, 1, 2, ....
Substitute in parallel all elements in r which equal (according to pred) ss[2*n] with ss[2*n + 1] for n = 0, 1, 2, ....
Lazy Substitution Algorithms.
See also: http://forum.dlang.org/post/pymxzazxximtgixzbnpq@forum.dlang.org