4 ms·

Heh, the kragen[hashmap] comes through. Thanks for the quote. While those are interesting, probably in the same way that Shen is interesting, I was thinking mo

• kragen 6y ago
  That sounds like the insight cdiggins based Cat's type system on, but I'm not entirely sure in part because I don't really understand Cat's type system. As an example, though, for the code popop = { pop pop} Cat infers the parametrically polymorphic typing judgment popop : ('t0 't1 't2 -> 't2) where 't2 is the type of the rest of the stack, I guess, and juxtaposition of types is a sort of product operation (noncommutative, but I think associative, and thus perhaps a monoid). Not sure what you mean about "projectional" — do you mean that "pop" is a "projection" in the relational sense, in that it maps, for example, the stack 3 8 1 (with the top on the left) and the stack 7 8 1 to the same resulting stack state 8 1? I don't know anything about protein folding. > I still haven't grokked your whole description of your Lisp reader, I'll have to sleep on it. Is it related in structure to the METAII meta compiler or parser combinators? Well, I didn't really write much of a description of the reader. It's a recursive-descent predictive parser, same as Probst's reader, and probably most Lisp readers. READ sets up the input pointers and calls (READ), which is ((READ)), which discriminates between lists and atoms (which are numbers) by looking for a "(". If it doesn't find one, it calls READ-NUM to read a number. But if it does, it calls READ-TAIL, which recursively reads the list contents (by calling (READ)) until it finds a ")", then returns back up, consing up the list as it goes. Probst's code works the same way, with the correspondences READ ↔ LISP-LOAD-FROM-STRING, (READ) ↔ LISP-READ-LISP, ((READ)) ↔ _LISP-READ-LISP, READ-NUM ↔ LISP-READ-TOKEN/-NUMBER/-SYMBOL, and READ-TAIL ↔ LISP-READ-LIST. META II has the similarity that it generates recursive-descent parsers with predictive parsing, but the dissimilarity that it's a domain-specific language for writing parsers. Parser combinators are a technique for embedding any domain-specific parsing language in a general-purpose host language, regardless of what parsing algorithm is used, though Packrat may be the most common choice, and Packrat has certain similarities to recursive-descent parsing. Is that helpful?
  • tsegratis 6y ago
    Very
  • sitkack 6y ago
    > Is that helpful? Absolutely. It made my day. Thank you.
  • DonHopkins 6y ago
    You could follow Lisp's car/caar/caaar cdr/cddr/cdddr cdadar/cadadar/caaddaar naming conventions in Forth ("waiting for the other shoe to drop") or PostScript ("waiting for the other shoe to pop"): Forth: : droop drop drop ; : drooop drop drop drop ; : droooop drop drop drop drop ; PostScript: /poop { pop pop } def /pooop { pop pop pop } def /poooop { pop pop pop pop } def
    • kragen 6y ago
      If you were to implement such a PostScript-based programming language for a Racal PDP-11 clone (or an HP calculator, or a P-code machine), whether in NoCal or in SoCal, I think you'd have to call it FECAL. If you really wanted to provide such a set of operators for, say, the top N stack items, you could give them systematic names with some distinctive scheme; limiting such stack operators to the top 3, for example, with no more than 2 extra results, you could provide the operators x→ (drop), x→x (nop), x→xx (bad Mexican beer), x→xxx (dupup), xy→ (2drop), xy→x (nip), xy→y (drop again, for consistency), xy→xx (nip dup), xy→xy (nop), xy→yx (exch†), xy→yy (drop dup), xy→xxx (nip dup dup), xy→xxy (dup again), xy→xyx (tuck), xy→xyy, xy→yxx, xy→yxy, xy→yyx, xy→yyy, xy→xxxx, xy→xxxy, xy→xxyx, xy→xxyy, xy→xyxx, xy→xyxy, xy→xyyx, xy→xyyy, xy→yxxx, xy→yxxy, xy→yxyx, xy→yxyy, xy→yyxx, xy→yyxy, xy→yyyx, xy→yyyy, xyz→, xyz→x, xyz→y, xyz→z, xyz→xx, xyz→xy (condescending answer on Stack Overflow), xyz→xz, xyz→yx, xyz→yy, xyz→yz, xyz→zx, xyz→zy, xyz→zz, xyz→xxx (programmers over 18 only), xyz→xxy (Klinefelter syndrome), xyz→xxz, xyz→xyx, xyz→xyy (Jacobs syndrome), xyz→xyz, xyz→xzx, xyz→xzy, xyz→xzz, xyz→yxx, xyz→yxy, xyz→yxz, xyz→yyx, xyz→yyy (bargaining, denial), xyz→yyz, xyz→yzx, xyz→yzy, xyz→yzz, xyz→zxx, xyz→zxy, xyz→zxz, xyz→zyx, xyz→zyy, xyz→zyz, xyz→zzx, xyz→zzy, xyz→zzz, xyz→xxxx, xyz→xxxy, xyz→xxxz, xyz→xxyx, xyz→xxyy, xyz→xxyz, xyz→xxzx, xyz→xxzy, xyz→xxzz, xyz→xyxx, xyz→xyxy, xyz→xyxz, xyz→xyyx, xyz→xyyy, xyz→xyyz, xyz→xyzx, xyz→xyzy, xyz→xyzz, xyz→xzxx, xyz→xzxy, xyz→xzxz, xyz→xzyx, xyz→xzyy, xyz→xzyz, xyz→xzzx, xyz→xzzy, xyz→xzzz, xyz→yxxx, xyz→yxxy, xyz→yxxz, xyz→yxyx, xyz→yxyy, xyz→yxyz, xyz→yxzx, xyz→yxzy, xyz→yxzz, xyz→yyxx, xyz→yyxy, xyz→yyxz, xyz→yyyx, xyz→yyyy, xyz→yyyz, xyz→yyzx, xyz→yyzy, xyz→yyzz, xyz→yzxx, xyz→yzxy, xyz→yzxz, xyz→yzyx, xyz→yzyy, xyz→yzyz, xyz→yzzx, xyz→yzzy, xyz→yzzz, xyz→zxxx, xyz→zxxy, xyz→zxxz, xyz→zxyx, xyz→zxyy, xyz→zxyz, xyz→zxzx, xyz→zxzy, xyz→zxzz, xyz→zyxx, xyz→zyxy, xyz→zyxz, xyz→zyyx, xyz→zyyy, xyz→zyyz, xyz→zyzx, xyz→zyzy, xyz→zyzz, xyz→zzxx, xyz→zzxy, xyz→zzxz, xyz→zzyx, xyz→zzyy, xyz→zzyz, xyz→zzzx, xyz→zzzy, xyz→zzzz (sleep 4), xyz→xxxxx, xyz→xxxxy, xyz→xxxxz, xyz→xxxyx, xyz→xxxyy, xyz→xxxyz, xyz→xxxzx, xyz→xxxzy, xyz→xxxzz, xyz→xxyxx, xyz→xxyxy, xyz→xxyxz, xyz→xxyyx, xyz→xxyyy, xyz→xxyyz, xyz→xxyzx, xyz→xxyzy, xyz→xxyzz, xyz→xxzxx, xyz→xxzxy, xyz→xxzxz, xyz→xxzyx, xyz→xxzyy, xyz→xxzyz, xyz→xxzzx, xyz→xxzzy, xyz→xxzzz, xyz→xyxxx, xyz→xyxxy, xyz→xyxxz, xyz→xyxyx, xyz→xyxyy, xyz→xyxyz, xyz→xyxzx, xyz→xyxzy, xyz→xyxzz, xyz→xyyxx, xyz→xyyxy, xyz→xyyxz, xyz→xyyyx, xyz→xyyyy, xyz→xyyyz, xyz→xyyzx, xyz→xyyzy, xyz→xyyzz, xyz→xyzxx, xyz→xyzxy, xyz→xyzxz, xyz→xyzyx, xyz→xyzyy, xyz→xyzyz, xyz→xyzzx, xyz→xyzzy (Nothing happens), xyz→xyzzz, xyz→xzxxx, xyz→xzxxy, xyz→xzxxz, xyz→xzxyx, xyz→xzxyy, xyz→xzxyz, xyz→xzxzx, xyz→xzxzy, xyz→xzxzz, xyz→xzyxx, xyz→xzyxy, xyz→xzyxz, xyz→xzyyx, xyz→xzyyy, xyz→xzyyz, xyz→xzyzx, xyz→xzyzy, xyz→xzyzz, xyz→xzzxx, xyz→xzzxy, xyz→xzzxz, xyz→xzzyx, xyz→xzzyy, xyz→xzzyz, xyz→xzzzx, xyz→xzzzy, xyz→xzzzz, xyz→yxxxx, xyz→yxxxy, xyz→yxxxz, xyz→yxxyx, xyz→yxxyy, xyz→yxxyz, xyz→yxxzx, xyz→yxxzy, xyz→yxxzz, xyz→yxyxx, xyz→yxyxy, xyz→yxyxz, xyz→yxyyx, xyz→yxyyy, xyz→yxyyz, xyz→yxyzx, xyz→yxyzy, xyz→yxyzz, xyz→yxzxx, xyz→yxzxy, xyz→yxzxz, xyz→yxzyx, xyz→yxzyy, xyz→yxzyz, xyz→yxzzx, xyz→yxzzy, xyz→yxzzz, xyz→yyxxx, xyz→yyxxy, xyz→yyxxz, xyz→yyxyx, xyz→yyxyy, xyz→yyxyz, xyz→yyxzx, xyz→yyxzy, xyz→yyxzz, xyz→yyyxx, xyz→yyyxy, xyz→yyyxz, xyz→yyyyx, xyz→yyyyy, xyz→yyyyz, xyz→yyyzx, xyz→yyyzy, xyz→yyyzz, xyz→yyzxx, xyz→yyzxy, xyz→yyzxz, xyz→yyzyx, xyz→yyzyy, xyz→yyzyz, xyz→yyzzx, xyz→yyzzy, xyz→yyzzz, xyz→yzxxx, xyz→yzxxy, xyz→yzxxz, xyz→yzxyx, xyz→yzxyy, xyz→yzxyz, xyz→yzxzx, xyz→yzxzy, xyz→yzxzz, xyz→yzyxx, xyz→yzyxy, xyz→yzyxz, xyz→yzyyx, xyz→yzyyy, xyz→yzyyz, xyz→yzyzx, xyz→yzyzy, xyz→yzyzz, xyz→yzzxx, xyz→yzzxy, xyz→yzzxz, xyz→yzzyx, xyz→yzzyy, xyz→yzzyz, xyz→yzzzx, xyz→yzzzy, xyz→yzzzz, xyz→zxxxx, xyz→zxxxy, xyz→zxxxz, xyz→zxxyx, xyz→zxxyy, xyz→zxxyz, xyz→zxxzx, xyz→zxxzy, xyz→zxxzz, xyz→zxyxx, xyz→zxyxy, xyz→zxyxz, xyz→zxyyx, xyz→zxyyy, xyz→zxyyz, xyz→zxyzx, xyz→zxyzy, xyz→zxyzz, xyz→zxzxx, xyz→zxzxy, xyz→zxzxz, xyz→zxzyx, xyz→zxzyy, xyz→zxzyz, xyz→zxzzx, xyz→zxzzy, xyz→zxzzz, xyz→zyxxx, xyz→zyxxy, xyz→zyxxz, xyz→zyxyx, xyz→zyxyy, xyz→zyxyz, xyz→zyxzx, xyz→zyxzy, xyz→zyxzz, xyz→zyyxx, xyz→zyyxy, xyz→zyyxz, xyz→zyyyx, xyz→zyyyy, xyz→zyyyz, xyz→zyyzx, xyz→zyyzy, xyz→zyyzz, xyz→zyzxx, xyz→zyzxy, xyz→zyzxz, xyz→zyzyx, xyz→zyzyy, xyz→zyzyz, xyz→zyzzx, xyz→zyzzy, xyz→zyzzz, xyz→zzxxx, xyz→zzxxy, xyz→zzxxz, xyz→zzxyx, xyz→zzxyy, xyz→zzxyz, xyz→zzxzx, xyz→zzxzy, xyz→zzxzz, xyz→zzyxx, xyz→zzyxy, xyz→zzyxz, xyz→zzyyx, xyz→zzyyy, xyz→zzyyz, xyz→zzyzx (Soda Springs), xyz→zzyzy, xyz→zzyzz, xyz→zzzxx, xyz→zzzxy, xyz→zzzxz, xyz→zzzyx, xyz→zzzyy, xyz→zzzyz, xyz→zzzzx, xyz→zzzzy, and xyz→zzzzz. You could certainly argue about the utility of many of these operators individually, not to say their mental risk as attractive nuisances, but their mnemonic value is indisputable. ______ † Where do you get an old PostScript printer? At an exch meet.