[Haskell-cafe] haltavista - look for functions by example

Roel van Dijk vandijk.roel at gmail.com
Sun Sep 19 13:41:21 EDT 2010

Very interesting!

It got me thinking: if you combine this with the Arbitrary class [1]
of QuickCheck you can use it check if you have defined a function that
is "equal" to an already defined function.

Let's say I write the following function:

  intMul ∷ Integer → Integer → Integer
  intMul x 0 = 0
  intMul x n = x + intMul x (n - 1)

No you can automatically apply this function to a list of 100
generated inputs to get a list of input output pairs. Feed this into
haltavista and it should tell you that you can replace your definition
with Prelude (*). While such an observation is certainly not a proof
it is still useful.

It would be a nice addition to a Haskell editor. Especially for those
new to the language.


1 - http://hackage.haskell.org/packages/archive/QuickCheck/2.3/doc/html/Test-QuickCheck-Arbitrary.html

More information about the Haskell-Cafe mailing list