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   screwlisp (screwtape@mastodon.sdf.org)'s status on Saturday, 18-Jan-2025 16:45:17 JST screwlisp

   Pratt
   so, I read this. https://dl.acm.org/doi/pdf/10.1145/512927.512931
   but I've never done this before, so I have been having trouble getting a vibe.
   A point Pratt mentions is that the central problem is that you can't get people to accept a prefix language like this:
   print + * 2 3 * 4 5
   (assuming + and * act on two elements)
   but there are these crazy #lisp people, that if you add overspecified brackets:
   (print (+ (* 2 3) (* 4 5)))
   Say they will happily read and write, and can understand this expression perfectly.

   • Embed this notice
     webhat (webhat@infosec.exchange)'s status on Saturday, 18-Jan-2025 17:16:32 JST webhat

     in reply to

     @screwtape isn't this called polish notation? I remember when I first learned bison/flex (GNU YACC/lex equivalent) it got me to write a polish notation calculator which was basically this

   • Embed this notice
     screwlisp (screwtape@mastodon.sdf.org)'s status on Saturday, 18-Jan-2025 17:16:32 JST screwlisp

     in reply to

     • webhat

     @webhat Yeah, I heard it called Polish notation as well, or prefix notation. The problem arises that people want to write factorial as 5! not ! 5 (maybe you could get a lisper to write (fact 5)), or worse, people including lispers want to write 2/3 and so forth.
     So each token has a nud (prefix notation host language thing to do) and a led (infix or left-binding host language thing to do), and you compare the current right binding power with tokens' left binding powers as you go.... or something

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     screwlisp (screwtape@mastodon.sdf.org)'s status on Saturday, 18-Jan-2025 18:34:26 JST screwlisp

     in reply to

     • Digital Mark λ 📚 🕹 💾 🥃
     • webhat
     • DougMerritt (log😅 = 💧log😄)

     @dougmerritt
     Well, I'm just being a bit slow working through, like, given the article's description of a parser, imagine I wanted to parse
     (- 1 + 2 * 3 / 4)
     I'm having more trouble than I thought writing a parser from the diagrams on page 47.

     Ah, I might have misread Pratt's line in the article about the unwritability of
     (= (+ (* a (^ b 2)) (* c (^ d 2))) (* 4 (sin (+ a b))))
     :
     "(But I have recently encountered some LISP users claiming the reverse, so I may be biased.)"
     @webhat @mdhughes

   • Embed this notice
     DougMerritt (log😅 = 💧log😄) (dougmerritt@mathstodon.xyz)'s status on Saturday, 18-Jan-2025 18:34:27 JST DougMerritt (log😅 = 💧log😄)

     in reply to

     • Digital Mark λ 📚 🕹 💾 🥃
     • webhat

     @screwtape @webhat
     Vaughn Pratt was himself a Lisp programmer, and implemented CGOL as a Maclisp reader.

     He was at Stanford and MIT, and Berkeley pre-Unix, so there's no reason to think he was aware of the 'dc' RPN arithmetic tool, and the paper you reference is earlier than HP's RPN handheld calculators, which had a very loyal following.

     But was there a specific question?

     P.S. "Polish notation" is the most common name (after 'postfix') for operators following operands, just as Reverse Polish Notation (RPN) is the most common name (after 'prefix') for operators preceding operands.

     'The description "Polish" refers to the nationality of logician Jan Łukasiewicz' but people in the early 20th century had a tough time with Polish names so they used a nickname.

     He was famous for multiple things, though, for instance continuous (real-) valued logic, which in a hypothetical infinitely precise analog computer would allow hypercomputation -- computation beyond what is possible for Turing machines.

     https://en.wikipedia.org/wiki/Polish_notation
     https://en.wikipedia.org/wiki/Jan_%C5%81ukasiewicz

     @mdhughes

   • Embed this notice
     Pat (mostlypat@mastodon.sdf.org)'s status on Saturday, 18-Jan-2025 18:38:46 JST Pat

     in reply to

     • webhat

     @screwtape @webhat I'm familiar with Reverse Polish Notation from FORTH, but for some reason I never realised there was a non-Reversed l version¡

     In the context of stacks (which FORTH is based on) RPN makes perfect sense, and the context of sexp (which LISP is based on) PN make perfect sense...but without some programming language reason, it just looks ridiculous

   • Embed this notice
     screwlisp (screwtape@mastodon.sdf.org)'s status on Saturday, 18-Jan-2025 18:39:26 JST screwlisp

     in reply to

     • webhat
     • Pat

     @mostlypat
     Oh no I said Polish but I meant reverse polish sorry o_o
     @webhat

   • Embed this notice
     Pat (mostlypat@mastodon.sdf.org)'s status on Saturday, 18-Jan-2025 18:44:07 JST Pat

     in reply to

     • webhat

     @screwtape @webhat
     Actually I think the example you posted was in PN, not in RPN?

     In RPN it would be: 4 5 * 2 3 * +

     (Push 4, push 5, push pop * pop, etc)

   • Embed this notice
     screwlisp (screwtape@mastodon.sdf.org)'s status on Saturday, 18-Jan-2025 18:45:11 JST screwlisp

     in reply to

     • webhat
     • DougMerritt (log😅 = 💧log😄)
     • Pat

     @mostlypat
     Okay, I've got it backwards twice or something @dougmerritt
     @webhat