[Haskell-cafe] find functions that produce / consume a type?

Eric Seidel eric at seidel.io
Sun Nov 11 14:45:43 UTC 2018

Hoogle does let you restrict the search to the output type by prefixing your query with “::”. For example, “:: Maybe a” produces a list of functions that return a Maybe. 


Unfortunately this doesn’t seem to work in the new Hoogle hosted at hoogle.haskell.org. 

Sent from my iPhone

> On Nov 9, 2018, at 04:59, Johannes Waldmann <johannes.waldmann at htwk-leipzig.de> wrote:
> Dear Cafe,
> can we automate something like the following
>  for any type  T  that appears in signatures (shown by haddock),
>  add (separate) lists of "functions that produce T",
>  "functions that consume T".
> Hoogle can type-search approximately, but
> * it would always (want to) match the full type AST
> (matching with a subtree incurs a penalty?),
> * and not distinguish between producer and consumer?
> E.g.,
> https://ndmitchell.com/downloads/slides-hoogle_finding_functions_from_types-16_may_2011.pdf
> Slide #29 "Per Argument Searching"
> uses "search arguments", "search results" -
> only to  merge the results immediately.
> Can we keep them separate?
> - J.W.
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