Andy Wingo scripsit: > My suggestion would be to remove all mention of "file-error?" and > "read-error?" from the report, and include in the larger report modules > which specify certain errors from those procedures.
I reconstruct the reasoning of the WG thus: First, we decided to accept the pragmatic wisdom of R5RS that only certain exceptional situations were required to be signalable in all implementations, namely when an input file cannot be opened as a port, when an EOF is detected in the middle of a datum, and when an attempt was made to create an unsupported type of environment. To these we added the fourth type, the simple error signaled by `error`. The next idea was that if an error could be signaled, it could be trapped. Finally, in order to be able to safely trap errors from a distance and still determine which of the four known types of error condition was involved, predicates that distinguished them were introduced. In the final vote, the environment-type predicate was omitted as insufficiently useful. > As it is, I think most implementations will (define (file-error? x) #t), That doesn't conform: returning #f would do so, though at the expense of utility. -- John Cowan co...@ccil.org http://www.ccil.org/~cowan C'est la` pourtant que se livre le sens du dire, de ce que, s'y conjuguant le nyania qui bruit des sexes en compagnie, il supplee a ce qu'entre eux, de rapport nyait pas. --Jacques Lacan, "L'Etourdit" _______________________________________________ Scheme-reports mailing list Scheme-reports@scheme-reports.org http://lists.scheme-reports.org/cgi-bin/mailman/listinfo/scheme-reports
