lookup f >>= \expected ->
let accST = (\(s,ts) e->infer e >>= \(s_,et)->pure (compose s_ s,ts++[et])) in
foldM accST (zero,[]) args >>= \(s1, argTs)->
lookup f >>= \expected ->
let accST = (\(s,ts) e->infer e >>= \(s_,et)->pure (compose s_ s,ts++[et])) in
foldM accST (zero,[]) args >>= \(s1, argTs)->