[Haskell] Hlist distribution -- compiler error in TIP

Frank frank at geoinfo.tuwien.ac.at
Sat Dec 24 11:45:46 EST 2005

I just got the Hlist distribution but could not compile the example files
With ghc 6.4 (I use ghci - in eclipse - I did not use ghc with the

I got the following compile time error on module TIP:

    Could not deduce (HType2HNat e l n1,
		      HDeleteAtHNat n1 l l'1,
		      HOccurs e (TIP l),
		      HOccurs e2 (TIP l'1))
      from the context (HOccurs e1 (TIP l),
			HType2HNat e1 l n,
			HDeleteAtHNat n l l',
			HOccurs e2 (TIP l'),
			HOccurs e2 (TIP l),
			HType2HNat e2 l n',
			HDeleteAtHNat n' l l'',
			HOccurs e1 (TIP l''))
      arising from use of `y' at
    Probable fix:
      add (HType2HNat e l n1,
	   HDeleteAtHNat n1 l l'1,
	   HOccurs e (TIP l),
	   HOccurs e2 (TIP l'1))
      to the type signature(s) for `tuple'
      or add an instance declaration for (HOccurs e (TIP l), HOccurs e2 (TIP
    In the definition of `tuple':
	tuple (TIP l)
		= let
		    x = hOccurs (TIP l)
		    l' = hDeleteAtProxy (toProxy x) l
		    y = hOccurs (TIP l')
		  in (x, y)

Can anybody quickly see, what is wrong?

Andrew U. Frank
Professor, Head of Department
Geoinformation and Cartography E127       phone: +43 1 588 01 12710
TU Vienna                                 secr. +43 1 588 01 12700
Gusshausstrasse 27-29                     fax +43 1 588 01 12799
A-1040 Vienna Austria                     cellular phone +43 676 41925 72

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