Normally I would make a macro, but I'm not sure if there is anything I need to do to tie it into the @ syntax. In the little writeup on 'in' it says it expands to a for/list with a begin/text. I haven't found any documentation on begin/text though. I should probably should try a similar expansion myself. <div class="gmail_quote">On Thu, Mar 4, 2010 at 2:14 PM, Jay McCarthy <<a href="mailto:jay.mccarthy@gmail.com">jay.mccarthy@gmail.com</a>> wrote: <blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;"> <div><div></div><div class="h5">On Thu, Mar 4, 2010 at 9:45 AM, Doug Williams <<a href="mailto:m.douglas.williams@gmail.com">m.douglas.williams@gmail.com</a>> wrote: > The template documentation in Web: PLT Web Applications includes a little > blurb about the in special form that wraps a for/list to make it easier to > use. Are there other helper forms for other binding forms. In particular, > are there any that wrap simple let or let-values? > > A real example from a template that generates Graphviz output: > > The following uses in and looks nice. It binds the values and generates the > line for each query result. > > @in[(action-class-id action-class-label) (in-query `(action-class ,rule-id > ?id ?label))]{ > "@|rule-id|":"action-class" -> "@|action-class-id|" [style=dashed]; > } > > But, since there should be exactly one result to that query and there is a > lighter-weight function, query-values, that has more appropriate semantics - > in particular, it will generate an error if there is not exactly one result, > I'd rather use let-values than the sequencing form. > > @let-values[(((action-class-id action-class-label) (query-values > `(action-class ,rule-id ?id ?label))))]{ > @list{ > "@|rule-id|":"action-class" -> "@|action-class-id|" [style=dashed]; > }} > > works just fine, but is rather cumbersome. Is there a better way to write > this using @ syntax? </div></div>If you limit yourself to one body, you could use a macro like: (let-values-ish [(a b) expr] ... expr) You could parse a little more and make (let-values-ish (a b) expr ... expr) work. But I haven't written either of these or something like it. Jay > > Doug > > _________________________________________________ > For list-related administrative tasks: > <a href="http://list.cs.brown.edu/mailman/listinfo/plt-scheme" target="_blank">http://list.cs.brown.edu/mailman/listinfo/plt-scheme</a> > > -- Jay McCarthy <<a href="mailto:jay@cs.byu.edu">jay@cs.byu.edu</a>> Assistant Professor / Brigham Young University <a href="http://teammccarthy.org/jay" target="_blank">http://teammccarthy.org/jay</a> "The glory of God is Intelligence" - D&C 93 </blockquote></div>