Hi, I must start by saying, that I don't have any knowledge about ghc internals. Performance of haskell programs seems to me heavily depended on the data structures of a simple linked lists. Because of the amount of cons-cells, simple linked lists aren't very GC-friendly. There is a paper about a replacement, called VLists. http://icwww.epfl.ch/publications/documents/IC_TECH_REPORT_200244.pdf So maybe VLists could be used in haskell internally for lists and strings. Best regards, Christoph Bauer Dipl. Inf. LMS Deutschland GmbH Luxemburgerstr. 7 D-67657 Kaiserslautern T +49 631 303 22 152 mailto:Christoph.Bauer@lms-gmbh.de http://www.lmsintl.com