Memory Management – What Happens When Both Heap and Stack Are Full?

Unfortunately there are cases when one has to use seq in order to get a efficient/well working program for large data. So in many cases, you cannot do without it in production code. You can find more information in Real World Haskell, Chapter 25. Profiling and optimization.

However, there are possibilities how to avoid using seq directly. This can make code cleaner and more robust. Some ideas:

1. Use conduit, pipes or iteratees instead of interact. Lazy IO is known to have problems with managing resources (not just memory) and iteratees are designed exactly to overcome this. (I'd suggest to avoid lazy IO alltogether no matter how large your data is - see The problem with lazy I/O.)
2. Instead of using seq directly use (or design your own) combinators such as foldl' or foldr' or strict versions of libraries (such as Data.Map.Strict or Control.Monad.State.Strict) that are designed for strict computations.
3. Use BangPatterns extension. It allows to replace seq with strict pattern matching. Declaring strict constructor fields could be also useful in some cases.
4. It's also possible to use Strategies for forcing evaluation. Strategies library is mostly aimed at parallel computations, but has methods for forcing a value to WHNF (rseq) or full NF (rdeepseq) as well. There are many utility methods for working with collections, combining strategies etc.

I agree that "dynamic" is a poor choice of words, but we're stuck with it now. It basically means the memory allocation is done explicitly by the programmer, using something like new or malloc, instead of automatically by the programming language, as in a function's local variables.