Arc Forum | In Arc I sometimes like to say (a.b:c.d e f), which this change breaks. But I do...

Arc Forum

2 points by rocketnia 4866 days ago | link | parent

In Arc I sometimes like to say (a.b:c.d e f), which this change breaks. But I don't mind that. ^_^

Anyway, what you're talking about is already how Penknife works: Infix operators on the right are always handled first. An interesting result is that a!b ssyntax is a bit redundant under this setup. Here's an Arc demonstration:

  ; with ! ssyntax
  a.b!c.d        ->  (a.b!c d)
                 ->  ((a.b (quote c)) d)
  
  ; without ! ssyntax
  a.b:quote.c.d  ->  (a.b:quote.c d)
                 ->  ((a.b:quote c) d)
                 ->  (((compose a.b quote) c) d)
                 ->  ((a.b (quote c)) d)

So now the following ssyntaxes are all abbreviations for things that are a little more verbose but just as edit-efficient:

  a!b  -> a:quote.b
  .a   -> get.a
  !a   -> get:quote.a
  ~a   -> no:a

The ssyntaxes left over are a:b, a.b, and a&b.

In Penknife, I've been thinking about having infix operator such that a`b.c is (b a c). Arc could do this if a`b expanded to something like (opcurry b a), where 'opcurry was a metafn such that ((opcurry a b c) d e f) expanded to (a b c d e f). Then the only essential ssyntaxes would be a`b and a.b:

  a&b  -> a`andf.b
  a:b  -> a`compose.b
  a!b  -> a`compose.quote.b
  .a   -> get.a
  !a   -> get`compose.quote.a
  ~a   -> no`compose.a

Of course, at a certain point the verbosity is a bit silly. I've defined ` as a curry function in Penknife so that I can test it out a`foo.b with everyday functions foo, like 1`+.2 and so forth, and I've found it pretty cumbersome to actually type. Still, it's less cumbersome than 1.+(2), I suppose. :-p

Maybe it'll be useful in an axiomatic way. Perhaps a Penknife-like or Arc-like language can have ` and . as its only basic infix operators, with all other infix operators being abbreviations defined in terms of those two....

Hmm, an alternate axiomatic approach is to treat a`b.c as a single ternary operator a{b}c.

  a&b  -> a{andf}b
  a:b  -> a{compose}b
  a.b  -> a{call-op}b  ; where (call-op a b) expands to (a b)
  a!b  -> a{compose}quote{call-op}b
  .a   -> get{call-op}a
  !a   -> get{compose}quote{call-op}a
  ~a   -> no{compose}a

This is essentially equivalent to Penknife's approach, except that Penknife uses Haskell-style naming rules (infix identifier or alpha identifier) rather than delimiters. So it looks like the a`b.c approach is just a way to simulate this syntax system within itself. Pretty interesting. XD