On 09/09/2011, at 8:19 PM, John Lato wrote:
Agreed. Whenever I'd like to use mapM (or any other function for which a *M_ is available), I've found the following rules helpful:
1. If I can guarantee the list is short (~ n<=20), go ahead and use mapM 2. Otherwise use mapM_, foldM_, or foldM if a real reduction is possible (i.e. not "foldM snocM []").
Step 2 sometimes requires changing my design, but it's always been for the better. `mapM_` tends to require more pipeline composition, so it's leveraging the language's strengths.
This thread is really interesting - it relates directly to problems I am currently having with mapM over large lists (see the thread "stack overflow pain"). Can you explain what you mean by "mapM_ tends to require more pipeline composition"? In what way is it leveraging the language strengths? Thanks, Tim