fix fold_ function
with small whole results (in contrast with lazily-generated list or large
lists where only a part is consumed.)
"%m
- = fun op nul list => %deep_seq% (foldl op nul list),
+ = fun op nul list => array.foldl op nul list,
imap0: forall a b. (Num -> a -> b) -> (Array a) -> (Array b)
| doc m%%"
