The day after I wrote this message I wrote such a macro myself -- because it was natural to dispatch on the shape of parentheses. But I will never have to scribble about this one; it just generates HTML for my course.
But I agree that keywords are much better for this purpose. They wouldn't have worked in my case. My syntax comes from a string and I use it both ways. -- Matthias On Nov 20, 2012, at 9:05 PM, Neil Toronto wrote: > (Probably. Why are we whispering?) > > Anyway, it occurred to me that I need to provide a more robust way to > generate code for literal arrays anyway. Keywords are more easily preserved > by macros than syntax properties: > > (array (array-row 0 1 2 3)) > > I think that'll let me use Eli's sneaky eval:alts to display (array [0 1 2 > 3]) but evaluate (array (array-row 0 1 2 3)). > > Neil ⊥ > > On 11/18/2012 08:12 PM, Matthias Felleisen wrote: >> >> (Perhaps this suggests a problem with making a macro depend on the shape of >> parens around a sub-expression.) >> >> >> >> >> On Nov 18, 2012, at 10:01 PM, Neil Toronto wrote: >> >>> I'm writing the documentation for math/array, and the examples all fail. >>> Here's a simple one: >>> >>> @examples[#:eval untyped-eval >>> (array [0 1 2 3])] >>> >>> The evaluator raises this error: >>> >>> application: not a procedure; >>> expected a procedure that can be applied to arguments >>> given: 0 >>> arguments...: >>> 1 >>> 2 >>> 3 >>> >>> The problem here is that the `array' macro is sensitive to square brackets, >>> but Scribble doesn't preserve the 'paren-shape syntax property. (Either >>> that, or `examples' only sends lists to the evaluator, not syntax.) So >>> (array [0 1 2 3]) gets evaluated as (array (0 1 2 3)), which looks like a >>> zero-dimensional array containing (0 1 2 3), which is an application of the >>> value `0'. Bad. >>> >>> I know this can work just fine; for example, this does the expected thing >>> in the REPL: >>> >>> > (eval #'(require math)) >>> > (eval #'(array [0 1 2 3])) >>> (array [0 1 2 3]) >>> >>> Is there a way to get Scribble to behave like I expect? >>> >>> Neil ⊥ >>> _________________________ >>> Racket Developers list: >>> http://lists.racket-lang.org/dev >> >
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