Monad Factory: Type-Indexed Monads

  • Mark Snyder
  • Perry Alexander
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 6546)


Monads provide a greatly useful capability to pure languages in simulating side-effects, but implementations such as the Monad Transformer Library [1] in Haskell prohibit reuse of those side-effects such as threading through two different states without some explicit work-around. Monad Factory provides a straightforward solution for opening the non-proper morphisms by indexing monads at both the type-level and term-level, allowing ‘copies’ of the monads to be created and simultaneously used within even the same monadic transformer stack. This expands monads’ applicability and mitigates the amount of boilerplate code we need for monads to work together, and yet we use them nearly identically to non-indexed monads.


monads Haskell type-level programming 


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Copyright information

© Springer-Verlag Berlin Heidelberg 2011

Authors and Affiliations

  • Mark Snyder
    • 1
  • Perry Alexander
    • 1
  1. 1.Information and Telecommunication Technology CenterThe University of KansasLawrenceUSA

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