[CM] Help sought for a macro

[Iain Duncan]

thanks Christos. I guess my one liner example was not clear, it's not infix
notation, it's still prefix notation, just as one whitespace and token
separated call. As in, the first slot in each ~> delimited s-exp is still a
function call, the parens are just implied. I imagine it's not of use to
anyone outside of Max, but it will be very useful in that context. To
clarify what I meant, this is probably a better example:

(x ~> fun1 arg1 _ ~> fun2 _ arg2 arg3)
would execute the same as
(chain (eval x) (fun1 arg1 _) (fun2 _ arg2 arg3) )
which is also equivalent to
(fun2 (fun1 arg1 (eval x)) arg2 arg3)

so it's really just a way to write chains without having parens in there,
the reason being that lists in messages with max are very easy to work with
when they are all whitespace separated tokens, and allow interpolation with
max's built in tools. So it allows people to make s4m "one-liners" that
replace a whole wack of max objects for some use cases, and have access to
s4m variables.

iain


On Sat, Sep 19, 2020 at 1:13 PM Christos Vagias <chris.actondev at gmail.com>
wrote:

> Hi Iain,
>
> Wasn't aware of the chain srfi. Interesting.
> Since I'm coming more from clojure I guess I'll focus a bit more on the
> "as->", "->" and "->>".
> Could try fiddling with these from Monday on and will keep you posted on
> the process.
>
> The "(x ~> a _ b ~> c _ )" form seems kinda too much though, adding infix
> notation to the mix
>
> On Sat, 19 Sep 2020 at 19:37, Iain Duncan <iainduncanlists at gmail.com>
> wrote:
>
>> Hi colleagues, I'm trying to figure out how to build a couple of
>> threading macros that would be very helpful in Max/MSP for Scheme for Max,
>> but it is frankly over my head right now. Working it out will be a good
>> exercise but I figured I would post here in case this is trivial for some
>> macro experts in S7 and they are willing to share something I can study.
>>
>> I want to implement something like srfi-197, where it is called "chain".
>> (but srfi-197 uses syntax-case and syntax-rules)
>>
>> so from the docs there:
>>
>> (chain x (a b _)) ; => (a b x)
>> (chain (a b) (c _ d) (e f _)) ; => (let* ((x (a b)) (x (c x d))) (e f x))
>> (chain (a) (b _ _) (c _)) ; => (let*-values (((x1 x2) (a)) ((x) (b x1 x2))) (c x))
>>
>>
>> But what I'd really to make on top of that is a version for allows one to
>> use this for one liners in Max without inner parens, so something like
>> this, where the macro is ~>
>>
>> (x ~> a _ b ~> c _ )
>> becomes something  equivalent of:
>> (c (a (eval x) b))
>>
>> Because Scheme for Max will take a max message and treat it as code to be
>> wrapped in outer parens and then eval'd, this will let people do very
>> useful things in one short max message (where say $i and $i2 come from
>> another max message sending to it:
>>
>> $i1 ~> + 10 _ ~> / $i2 _
>>
>> If anyone has suggestions or feels like helping that would be amazing.
>> thanks!
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>>
>
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