Question: Can I manipulate 1G strings in Haskell? Short answer: Yes! Mostly. Doing some stress testing of FPS, here are some results for 1G strings. 3.2Ghz box, 2G physical mem. Size of input string: 1G N.B. 2G of physical ram is not enough when trying to benchmark functions that copy 1G strings around :) Function Time in seconds All O(1) functions: length O index 0 head 0 tail 0 last 0 init 0 O(n) , but answer found early on: compare 0 any 0 all 0 elem 0 elemIndex 0 O(n) mostly: maximum 3.855 minimum 4.666 filterChar 8.084 elemIndicies 11.504 lines 12.247 find 14.046 tails 27.328 inits 33.620 words 100.963 map toUpper 143.871 Failed due to memory exhaustion. Almost made it though, just need a tad more ram than I had. filter ! unlines ! unwords ! reverse ! -- copy cons ! -- copy snoc ! -- involves a copy ++ ! -- can't concat two 1G strings on this box sort ? taking too long, but space was ok. [Char] functions are much more costly. pack ! -- constructing 1G [Char] is not ok. unpack ! Lesssons, you can play with 1G strings in Haskell. Having more than 2G ram is useful though. Replacing higher order functions with hard coded first order equivalents can help. -- Don