Web Interface for CASS

Residuation analysis

This analysis checks whether a function does not residuate and yields, if it successfully evaluates to some value, a ground value provided that the function is called with some ground values as arguments.

To bemore precise, the analysis associates to each function one of the following results:

• NoResiduateIf xs (does not residuate if arguments xs are ground):
  If the operation is called where the arguments in the index list xs are ground values (where arguments are numbered from 1), then the evaluation does not residuate and yields a ground value. For instance, the operation
  const :: a -> b -> a const x _ = x
  has the residuation behavior NoResiduateIf [1], and the list concatenation ++ has the residuation behavior NoResiduateIf [1,2].
• MayResiduate (possible residuation or non-ground result):
  The operation might residuate or yields a non-ground value, independent of the arguments. For instance, this is the case for the operations
  f x = x + ensureNotFree unknown
  g x = (x,y) where y free
• NoResInfo (unknown residuation behavior):
  The residuation behavior of this function cannot be determined. This might occur when complex recursive lets are involved.