Hi,

You don't know anything about your a's but that they have FromJSON instances. That in turn means you can get values from aeson parsing functions. Think parseJSON :: Value -> Parser a

Could you be more specific about the problem you try to solve? 

Best
Jan

Baa <aquagnu@gmail.com> schrieb am Di., 1. Aug. 2017, 10:32:
Hello, List!

I have, for example, function with signature like

  fn :: FromJSON a => Map Text a -> BlahBlah

and I want to treat this `a` as String (or `Text`), to read it with
`readMaybe`. Am I right that it's impossible? I get error about "...a
is rigid type and could not be matched with Text...". But `Text` is
`FromJSON` instance. Is it possible to do it (cast, convert, unwrap, etc)?

The problem's source is that early I worked with `Text` values only
(getting from HTML form) but now they become any type: int's, bool's,
etc).

===
Best regards,
  Paul
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