Having just read that book, it's not that laziness is bad or good for data structure performance. It's mostly that you can't use a data structure designed for o

Having just read that book, it's not that laziness is bad or good for data structure performance. It's mostly that you can't use a data structure designed for one paradigm with the other and expect the same performance characteristics. Laziness can make things faster (I think the CatenableQueue was a good example of this), but it can also make things slower (take your pick of examples). In all I guess I'm not disagreeing with you at all, I just wanted to provide a bit more context and get some more use out of that book.