All, All this talk about Mathematica and a reference to monadic treatments of backtracking reminded me that a year ago i was involved in work on a Mathematica-like widget. At the time i noticed that a good deal of the structure underlying LP, SAT and other solvers was terribly reminiscent of comprehension-style monadic structure. i think i asked Erik Meijer if he knew of any work done on this and posted to LtU, but nobody seemed to have understood what i was mumbling about. So, let me try here: does anybody know of references for a monadic treatment of constraint satisfaction? BTW, i think this could have a lot of bang-for-buck because the literature i read exhibited two basic features: - the "standard" treatments (even by CS-types) are decidedly not compositional - the people in the field who face industrial strength csp problems report that they have to take compositional approaches because the problems are just too large otherwise (both from a human engineering problem as well as a computational complexity problem) Best wishes, --greg -- L.G. Meredith Managing Partner Biosimilarity LLC 505 N 72nd St Seattle, WA 98103 +1 206.650.3740 http://biosimilarity.blogspot.com