[Haskell-beginners] Parser using the show method

[PICCA Frederic-Emmanuel]

Hello,

I have a data type like this

data SpaceGroup = P1 | P2 | P21 | C2 | P222 | P2221 | P21212 | P212121 | C222 | C2221 | F222 | I222 | I212121 | P4 | P41 | P42 | P43 | P422 | P4212 | P4122 | P41212 | P4222 | P42212 | P4322 | P43212 | I4 | I41 | I422 | I4122 | P3 | P31 | P32 | P312 | P321 | P3112 | P3121 | P3212 | P3221 | P6 | P61 | P62 | P63 | P64 | P65 | P622 | P6122 | P6522 | P6222 | P6422 | P6322 | R3 | R32 | P23 | P213 | P432 | P4232 | P4332 | P4132 | F23 | F432 | F4132 | I23 | I213 | I432 | I4132
    deriving (Show)

has you can see it is quite long.

I want to write a method in order to parser a string using the show method.

myparser :: Parser SpaceGroup
myparser = do
    ...

I do not want to write for each constructor something like

do
   t <- takeText
   if t == "P21" then P21 else ...

thanks for your help

Frederic