Henning Thielemann
Sometimes I believed that I understand this reason, but then again I do not understand. I see that left-associative (++) like in ((a0 ++ a1) ++ a2) ++ a3 would cause quadratic time. But (++) is right-associative and 'concat' is 'foldr'. They should not scan the leading lists more than once. Also http://en.wikipedia.org/wiki/Difference_list doesn't answer this question. Where exactly is the problem?
| The shows functions return a function that prepends the output String | to an existing String. This allows constant-time concatenation of | results using function composition. I figure it's (constant vs. linear) vs. (linear vs. quadratic), for more involved examples. -- (c) this sig last receiving data processing entity. Inspect headers for past copyright information. All rights reserved. Unauthorised copying, hiring, renting, public performance and/or broadcasting of this signature prohibited.