Er? Refactoring the grammar like that is the clean and preferred
way. But if you insist, use the try combinator.

Oh, all right, i was trying to be loyal to the BNF in standard.

structuredTypeDef = try recordDef <|> recordOfDef

--
brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allbery@kf8nh.com
system administrator [openafs,heimdal,too many hats] allbery@ece.cmu.edu
electrical and computer engineering, carnegie mellon university KF8NH