On a Tighter Integration of Functional and Logic Programming

On the correctness of pull-tabbing

“…If eventually the choice is reduced to either of its alternatives every other choice with the same identifier must be reduced to the same alternative. A very similar idea in a rather different setting is proposed in (Brassel and Huch 2007;Brassel 2011). A pull-tab step clones a single node, a predecessor of the choice being pulled up.…”

KiCS2: A New Compiler from Curry to Haskell

“…In addition to the different search strategies to evaluate top-level expressions, our system also contains a primitive operation With this primitive, the programmer can define its own search strategy or collect all non-deterministic values into a list structure for further processing [15].…”

“…In the introduction we already discussed the various efforts to implement functional logic languages, like the construction of abstract machines [9,27,32] and the compilation into Prolog [5] or Haskell [13,15,16]. Our benchmarks show that an efficient implementation by compiling into a functional language depends on carefully handling the sharing of non-deterministic choices.…”

“…If one compiles into a non-strict functional language like Haskell, one can reuse the implementation of lazy evaluation and higher-order functions, but one has to implement non-deterministic evaluations [13,15]. Although Haskell offers list comprehensions to model backtracking [36], this cannot be exploited due to the specific semantical requirements of the combination of non-strict and non-deterministic operations [20].…”

“…We solve this problem by an explicit representation of non-deterministic values, i.e., we extend each data type by another constructor to represent the choice between several values. This idea is also the basis of the Curry implementation KiCS [15,16]. However, KiCS is based on unsafe features of Haskell that inhibit the use of optimizations provided by Haskell compilers like GHC.…”