yeah, trying to apply the idea unreasonably beyond its intent. Thanks for the replies folks. On Sunday, June 25, 2017 at 2:52:00 PM UTC-4, Alexis King wrote: > As written, the simple answer to your question is to use begin0 or > begin, depending on if you are using ~> or ~>>. > > > (~> 3 (begin0 (displayln "hi!")) (* 2)) > hi! > 6 > > But as Greg mentions, this is not very useful, and it probably isn’t > what you want, since the evaluated expression can only be evaluated for > side-effects, which is rather against the spirit of threading macros > altogether. > > It is a little difficult for me to imagine what a hypothetical syntax > for your use-case would look like without turning ~> into a much more > complicated binding form. As it is, the threading macros are all quite > simple, and they are simple shorthands for syntactic nesting. It would > be possible to generalize them quite a bit, but I am fond of their > simplicity, and I think Greg’s suggestion to just use let* is a good > one. I’m not sure there is a good way to synthesize the brevity and > simplicity of threading with a more powerful binding form, though if you > can come up with a syntax that accomplishes what you’re getting at, I’d > certainly at least be interested by it. > > > On Jun 25, 2017, at 09:44, Sanjeev Sharma wrote: > > > > is there a way to do a calculation in the middle of the chain that > > takes no arguments? In other words, exempt some operations in the > > chain from taking any arguments. > > > > Suppose one's doing a calculation of interest earned on an investment > > and one is threading a running balance through the chain, but at > > places one needs a calculation for purchases and/or dispositions to > > the investment.
-- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
