This example is 4 years old. In version 0.8.0 there was a implementation of many
in the Data.Attoparsec.Combinator
module, you can check the source here.
The current version of the library doesn't implements a many
function, but it implements a many'
function (source here). That's why you ghci
give you many'
as a suggestion.
The many
that was implemented in Data.Attoparsec.Combinator
is the same that is implemented in Control.Applicative
(see here the implementation of many
in the Alternative
type class). You probably need to import
the Control.Applicative
. If that works I would suggest that you make a pull request to solve that issue (the library repository is here)