I used foldl1 (+) because that's the literal translation of +/. I used (fromIntegral.length) instead of genericLength because genericLength requires an import (as does liftM2 actually, so I should've used that).
'Not much longer than APL's in terms of actual symbols used.' - well, there's liftM2, and for longer examples, chaining it is even worse - (f g h i j) in APL becomes liftM2 g f $ liftM2 i h j -> quickly becoming unwieldy and unclear.
A lot of people also seem to say 'oh well if each character was a word it would be the same', and while it seems like that might be true, in practice it isn't, and the use of symbols allows for pattern recognition that you just don't get with words.
You used monadic interface, instead you may use applicative interface.
liftM2 then become liftA2 and what you exemplify above (if I understand that correctly) will render as (g <$> f <*> (i <$> h <*> j)). It is unusual, because "g" goes before "f", but not much unusual. Note the explicit pure function application in the use of <$> and explicit apply <*>. I would like you and other readers compare that to the implicit apply in the "Are ours smaller than theirs?" paper I provided link above.
That translation shows what APL hides in its implicits.
Let me repeat. APL will certainly help you with computations over arrays but will most probably fail you big time with parsing of something like Ada. Haskell won't fail you in both cases at the expense of slightly more verbose program text.
Tacit programming exposes the need to "normalize" programs, to express them with as less function argument rearragement as possible. In stack based languages this is guided by the dependence on the stack(s) (data, return, control, whatever you invented). In point-free programming in Haskell, this is guided by argument capture and propagation. In K (I mostly studied it), as I understand it, tacit programming is guided by the implicit operations upon the stack of actual operations.
These variants of tacit programming are mostly the same, just some cases are more easily expressible or some operations conveniently assumed to be implicit.
'Not much longer than APL's in terms of actual symbols used.' - well, there's liftM2, and for longer examples, chaining it is even worse - (f g h i j) in APL becomes liftM2 g f $ liftM2 i h j -> quickly becoming unwieldy and unclear.
A lot of people also seem to say 'oh well if each character was a word it would be the same', and while it seems like that might be true, in practice it isn't, and the use of symbols allows for pattern recognition that you just don't get with words.