The Haskell corollary to Greenspun's 10th law: any sufficiently advanced type system includes an incomplete and twisted subset of Scheme. Tony. -- f.a.n.finch <dot at dotat.at> http://dotat.at/ FAIR ISLE: SOUTHEASTERLY 5 TO 7, OCCASIONALLY GALE 8 IN EAST. ROUGH OR VERY ROUGH. RAIN OR SHOWERS. MODERATE OR GOOD.