On Mon, May 10, 2010 at 12:44 PM, Matthew Flatt <mfl...@cs.utah.edu> wrote: > It seems there should be a way to make >> custom structs print as if they should be quoted, but that shouldn't >> be the default. > > I'm not sure about the default.
Here's the results of surveying uses of `prop:custom-write' in collects: 3 that shouldn't be quoted (1 of them by me) 3 that are not expressions, but are printed with () anyway, so should probably be made unreadable (all by me) 9 unreadable, so it shouldn't be quoted - 1 of these should be changed to a non-quoted form, probably (`set') 1 that has a pseudo-self-quoting syntax (srfi/63) This suggests that no one is writing custom printers that should be quoted. Further, since there's no mechanism for structs to automatically extend the read syntax and the behavior of `quote', only very rarely will structs be usefully printed in a quoted form. Both of these pieces of evidence suggest to me that quoting is the wrong default. > > Finally, one more things I noticed when looking at the custom-write > > docs: The following expression at the DrRacket repl errors with a > > strange error message: > > > > > #0='#(#0#) > > . read: #..= expressions not allowed in read-syntax mode > > > > This used to be allowed, right? > > This was allowed prior to v4.0, but not since v4.0. The error message is rather confusing - why does it mention `read-syntax'? -- sam th sa...@ccs.neu.edu _________________________________________________ For list-related administrative tasks: http://list.cs.brown.edu/mailman/listinfo/plt-dev
