(archive 'newLISPer)

June 27, 2008

Vacuum-tube Lisp

Filed under: newLISP — newlisper @ 17:33

I love the idea of a vacuum-tube computer running Lisp. Here’s Steve Russell:

I wrote the first implementation of a LISP interpreter on the IBM 704 at MIT in early in 1959.

The 704 family (704, 709, 7090) had “Address” and “Decrement” fields that were 15 bits long in some of the looping instructions. There were also special load and store instructions that moved these 15-bit addresses between memory and the index regiseters ( 3 on the 704, 7 on the others )

We had devised a representation for list structure that took advantage of these instructions.

Because of an unfortunate temporary lapse of inspiration, we couldn’t think of any other names for the 2 pointers in a list node than “address” and “decrement”, so we called the functions CAR for “Contents of Address of Register” and CDR for “Contents of Decrement of Register”.

After several months and giving a few classes in LISP, we realized that “first” and “rest” were better names, and we (John McCarthy, I and some of the rest of the AI Project) tried to get people to use them instead.

Alas, it was too late! We couldn’t make it stick at all. So we have CAR and CDR.

Like Steve, I much prefer first and rest to car and cdr. This approach is evident throughout newLISP, which usually leans towards a user-friendly and abbreviation-free approach to function naming.

But, although car and cdr have been uninspired for nearly 50 years, they have survived because they offer an extra geeky ability: you can add more a and d letters between the “c” and “r”, to produce functions with even weirder names. So caddr finds the car of the cdr of the cdr; you read from left to right, although the functions are applied from right to left as usual.

To be honest, I don’t know how I’ve managed to write any code at all in newLISP without having this readable and user-friendly syntax at my fingertips. So it’s time for newLISP to be ‘cdadderized’:

(define (car x) (first x))
(define (cdr x) (rest x))

(define (cdadderize x)
  (inc 'x)
  (set 'results '())
  (until (= x 0)
     (push   (% x 2) results)
     (set 'x (/ x 2)))
  (set 'results (rest results) 'f-name results)
  (map (fn (a b) (replace a results b)) '(0 1) '("(car " "(cdr "))
  (push (string "x"  (dup ")" (length results))) results -1)
  (set 'results (join results))
  (map (fn (a b) (replace a f-name b)) '(0 1) '("a" "d"))
  (letex ((fnm   (sym (string "c" (join f-name) "r")))
          (body results))
    (define (fnm x) (eval-string body))

(for (i 3 1022) (cdadderize i)) ; we did 1 and 2 :)

Not the prettiest code, but let’s run it and look at the new functions that have been defined:

(filter (fn (s)
    (and (starts-with  (name s) "ca|cd" 0)
         (ends-with (name s) "r")))
(caaaaaaaaaar caaaaaaaaadr caaaaaaaaar caaaaaaaadr caaaaaaaar caaaaaaadar caaaaaaaddr
caaaaaaadr caaaaaaar caaaaaadaar caaaaaadadr caaaaaadar caaaaaaddar caaaaaadddr
caaaaaaddr caaaaaadr caaaaaar caaaaadaaar caaaaadaadr caaaaadaar caaaaadadar caaaaadaddr
caaaaadadr caaaaadar caaaaaddaar caaaaaddadr caaaaaddar caaaaadddar caaaaaddddr
caaaaadddr caaaaaddr caaaaadr caaaaar caaaadaaaar caaaadaaadr caaaadaaar caaaadaadar
caaaadaaddr caaaadaadr caaaadaar caaaadadaar caaaadadadr caaaadadar caaaadaddar
caaaadadddr caaaadaddr caaaadadr caaaadar caaaaddaaar caaaaddaadr caaaaddaar caaaaddadar
caaaaddaddr caaaaddadr caaaaddar caaaadddaar caaaadddadr caaaadddar caaaaddddar
caaaadddddr caaaaddddr caaaadddr caaaaddr caaaadr caaaar caaadaaaaar caaadaaaadr
caaadaaaar caaadaaadar caaadaaaddr caaadaaadr caaadaaar caaadaadaar caaadaadadr
caaadaadar caaadaaddar caaadaadddr caaadaaddr caaadaadr caaadaar caaadadaaar caaadadaadr
caaadadaar caaadadadar caaadadaddr caaadadadr caaadadar caaadaddaar caaadaddadr
caaadaddar caaadadddar caaadaddddr caaadadddr caaadaddr caaadadr caaadar caaaddaaaar
caaaddaaadr caaaddaaar caaaddaadar caaaddaaddr caaaddaadr caaaddaar caaaddadaar
caaaddadadr caaaddadar caaaddaddar caaaddadddr caaaddaddr caaaddadr caaaddar caaadddaaar
caaadddaadr caaadddaar caaadddadar caaadddaddr caaadddadr caaadddar caaaddddaar
caaaddddadr caaaddddar caaadddddar caaaddddddr caaadddddr caaaddddr caaadddr caaaddr
caaadr caaar caadaaaaaar caadaaaaadr caadaaaaar caadaaaadar caadaaaaddr caadaaaadr
caadaaaar caadaaadaar caadaaadadr caadaaadar caadaaaddar caadaaadddr caadaaaddr
caadaaadr caadaaar caadaadaaar caadaadaadr caadaadaar caadaadadar caadaadaddr caadaadadr
caadaadar caadaaddaar caadaaddadr caadaaddar caadaadddar caadaaddddr caadaadddr
caadaaddr caadaadr caadaar caadadaaaar caadadaaadr caadadaaar caadadaadar caadadaaddr
caadadaadr caadadaar caadadadaar caadadadadr caadadadar caadadaddar caadadadddr
caadadaddr caadadadr caadadar caadaddaaar caadaddaadr caadaddaar caadaddadar caadaddaddr
caadaddadr caadaddar caadadddaar caadadddadr caadadddar caadaddddar caadadddddr
caadaddddr caadadddr caadaddr caadadr caadar caaddaaaaar caaddaaaadr caaddaaaar
caaddaaadar caaddaaaddr caaddaaadr caaddaaar caaddaadaar caaddaadadr caaddaadar
caaddaaddar caaddaadddr caaddaaddr caaddaadr caaddaar caaddadaaar caaddadaadr caaddadaar
caaddadadar caaddadaddr caaddadadr caaddadar caaddaddaar caaddaddadr caaddaddar
caaddadddar caaddaddddr caaddadddr caaddaddr caaddadr caaddar caadddaaaar caadddaaadr
caadddaaar caadddaadar caadddaaddr caadddaadr caadddaar caadddadaar caadddadadr
caadddadar caadddaddar caadddadddr caadddaddr caadddadr caadddar caaddddaaar caaddddaadr
caaddddaar caaddddadar caaddddaddr caaddddadr caaddddar caadddddaar caadddddadr
caadddddar caaddddddar caadddddddr caaddddddr caadddddr caaddddr caadddr caaddr
caadr caar cadaaaaaaar cadaaaaaadr cadaaaaaar cadaaaaadar cadaaaaaddr cadaaaaadr
cadaaaaar cadaaaadaar cadaaaadadr cadaaaadar cadaaaaddar cadaaaadddr cadaaaaddr
cadaaaadr cadaaaar cadaaadaaar cadaaadaadr cadaaadaar cadaaadadar cadaaadaddr cadaaadadr
cadaaadar cadaaaddaar cadaaaddadr cadaaaddar cadaaadddar cadaaaddddr cadaaadddr
cadaaaddr cadaaadr cadaaar cadaadaaaar cadaadaaadr cadaadaaar cadaadaadar cadaadaaddr
cadaadaadr cadaadaar cadaadadaar cadaadadadr cadaadadar cadaadaddar cadaadadddr
cadaadaddr cadaadadr cadaadar cadaaddaaar cadaaddaadr cadaaddaar cadaaddadar cadaaddaddr
cadaaddadr cadaaddar cadaadddaar cadaadddadr cadaadddar cadaaddddar cadaadddddr
cadaaddddr cadaadddr cadaaddr cadaadr cadaar cadadaaaaar cadadaaaadr cadadaaaar
cadadaaadar cadadaaaddr cadadaaadr cadadaaar cadadaadaar cadadaadadr cadadaadar
cadadaaddar cadadaadddr cadadaaddr cadadaadr cadadaar cadadadaaar cadadadaadr cadadadaar
cadadadadar cadadadaddr cadadadadr cadadadar cadadaddaar cadadaddadr cadadaddar
cadadadddar cadadaddddr cadadadddr cadadaddr cadadadr cadadar cadaddaaaar cadaddaaadr
cadaddaaar cadaddaadar cadaddaaddr cadaddaadr cadaddaar cadaddadaar cadaddadadr
cadaddadar cadaddaddar cadaddadddr cadaddaddr cadaddadr cadaddar cadadddaaar cadadddaadr
cadadddaar cadadddadar cadadddaddr cadadddadr cadadddar cadaddddaar cadaddddadr
cadaddddar cadadddddar cadaddddddr cadadddddr cadaddddr cadadddr cadaddr cadadr
cadar caddaaaaaar caddaaaaadr caddaaaaar caddaaaadar caddaaaaddr caddaaaadr caddaaaar
caddaaadaar caddaaadadr caddaaadar caddaaaddar caddaaadddr caddaaaddr caddaaadr
caddaaar caddaadaaar caddaadaadr caddaadaar caddaadadar caddaadaddr caddaadadr caddaadar
caddaaddaar caddaaddadr caddaaddar caddaadddar caddaaddddr caddaadddr caddaaddr
caddaadr caddaar caddadaaaar caddadaaadr caddadaaar caddadaadar caddadaaddr caddadaadr
caddadaar caddadadaar caddadadadr caddadadar caddadaddar caddadadddr caddadaddr
caddadadr caddadar caddaddaaar caddaddaadr caddaddaar caddaddadar caddaddaddr caddaddadr
caddaddar caddadddaar caddadddadr caddadddar caddaddddar caddadddddr caddaddddr
caddadddr caddaddr caddadr caddar cadddaaaaar cadddaaaadr cadddaaaar cadddaaadar
cadddaaaddr cadddaaadr cadddaaar cadddaadaar cadddaadadr cadddaadar cadddaaddar
cadddaadddr cadddaaddr cadddaadr cadddaar cadddadaaar cadddadaadr cadddadaar cadddadadar
cadddadaddr cadddadadr cadddadar cadddaddaar cadddaddadr cadddaddar cadddadddar
cadddaddddr cadddadddr cadddaddr cadddadr cadddar caddddaaaar caddddaaadr caddddaaar
caddddaadar caddddaaddr caddddaadr caddddaar caddddadaar caddddadadr caddddadar
caddddaddar caddddadddr caddddaddr caddddadr caddddar cadddddaaar cadddddaadr cadddddaar
cadddddadar cadddddaddr cadddddadr cadddddar caddddddaar caddddddadr caddddddar
cadddddddar cadddddddddr caddddddddr cadddddddr caddddddr cadddddr caddddr cadddr
caddr cadr car cdaaaaaaaar cdaaaaaaadr cdaaaaaaar cdaaaaaadar cdaaaaaaddr cdaaaaaadr
cdaaaaaar cdaaaaadaar cdaaaaadadr cdaaaaadar cdaaaaaddar cdaaaaadddr cdaaaaaddr
cdaaaaadr cdaaaaar cdaaaadaaar cdaaaadaadr cdaaaadaar cdaaaadadar cdaaaadaddr cdaaaadadr
cdaaaadar cdaaaaddaar cdaaaaddadr cdaaaaddar cdaaaadddar cdaaaaddddr cdaaaadddr
cdaaaaddr cdaaaadr cdaaaar cdaaadaaaar cdaaadaaadr cdaaadaaar cdaaadaadar cdaaadaaddr
cdaaadaadr cdaaadaar cdaaadadaar cdaaadadadr cdaaadadar cdaaadaddar cdaaadadddr
cdaaadaddr cdaaadadr cdaaadar cdaaaddaaar cdaaaddaadr cdaaaddaar cdaaaddadar cdaaaddaddr
cdaaaddadr cdaaaddar cdaaadddaar cdaaadddadr cdaaadddar cdaaaddddar cdaaadddddr
cdaaaddddr cdaaadddr cdaaaddr cdaaadr cdaaar cdaadaaaaar cdaadaaaadr cdaadaaaar
cdaadaaadar cdaadaaaddr cdaadaaadr cdaadaaar cdaadaadaar cdaadaadadr cdaadaadar
cdaadaaddar cdaadaadddr cdaadaaddr cdaadaadr cdaadaar cdaadadaaar cdaadadaadr cdaadadaar
cdaadadadar cdaadadaddr cdaadadadr cdaadadar cdaadaddaar cdaadaddadr cdaadaddar
cdaadadddar cdaadaddddr cdaadadddr cdaadaddr cdaadadr cdaadar cdaaddaaaar cdaaddaaadr
cdaaddaaar cdaaddaadar cdaaddaaddr cdaaddaadr cdaaddaar cdaaddadaar cdaaddadadr
cdaaddadar cdaaddaddar cdaaddadddr cdaaddaddr cdaaddadr cdaaddar cdaadddaaar cdaadddaadr
cdaadddaar cdaadddadar cdaadddaddr cdaadddadr cdaadddar cdaaddddaar cdaaddddadr
cdaaddddar cdaadddddar cdaaddddddr cdaadddddr cdaaddddr cdaadddr cdaaddr cdaadr
cdaar cdadaaaaaar cdadaaaaadr cdadaaaaar cdadaaaadar cdadaaaaddr cdadaaaadr cdadaaaar
cdadaaadaar cdadaaadadr cdadaaadar cdadaaaddar cdadaaadddr cdadaaaddr cdadaaadr
cdadaaar cdadaadaaar cdadaadaadr cdadaadaar cdadaadadar cdadaadaddr cdadaadadr cdadaadar
cdadaaddaar cdadaaddadr cdadaaddar cdadaadddar cdadaaddddr cdadaadddr cdadaaddr
cdadaadr cdadaar cdadadaaaar cdadadaaadr cdadadaaar cdadadaadar cdadadaaddr cdadadaadr
cdadadaar cdadadadaar cdadadadadr cdadadadar cdadadaddar cdadadadddr cdadadaddr
cdadadadr cdadadar cdadaddaaar cdadaddaadr cdadaddaar cdadaddadar cdadaddaddr cdadaddadr
cdadaddar cdadadddaar cdadadddadr cdadadddar cdadaddddar cdadadddddr cdadaddddr
cdadadddr cdadaddr cdadadr cdadar cdaddaaaaar cdaddaaaadr cdaddaaaar cdaddaaadar
cdaddaaaddr cdaddaaadr cdaddaaar cdaddaadaar cdaddaadadr cdaddaadar cdaddaaddar
cdaddaadddr cdaddaaddr cdaddaadr cdaddaar cdaddadaaar cdaddadaadr cdaddadaar cdaddadadar
cdaddadaddr cdaddadadr cdaddadar cdaddaddaar cdaddaddadr cdaddaddar cdaddadddar
cdaddaddddr cdaddadddr cdaddaddr cdaddadr cdaddar cdadddaaaar cdadddaaadr cdadddaaar
cdadddaadar cdadddaaddr cdadddaadr cdadddaar cdadddadaar cdadddadadr cdadddadar
cdadddaddar cdadddadddr cdadddaddr cdadddadr cdadddar cdaddddaaar cdaddddaadr cdaddddaar
cdaddddadar cdaddddaddr cdaddddadr cdaddddar cdadddddaar cdadddddadr cdadddddar
cdaddddddar cdadddddddr cdaddddddr cdadddddr cdaddddr cdadddr cdaddr cdaderizer
cdadr cdar cddaaaaaaar cddaaaaaadr cddaaaaaar cddaaaaadar cddaaaaaddr cddaaaaadr
cddaaaaar cddaaaadaar cddaaaadadr cddaaaadar cddaaaaddar cddaaaadddr cddaaaaddr
cddaaaadr cddaaaar cddaaadaaar cddaaadaadr cddaaadaar cddaaadadar cddaaadaddr cddaaadadr
cddaaadar cddaaaddaar cddaaaddadr cddaaaddar cddaaadddar cddaaaddddr cddaaadddr
cddaaaddr cddaaadr cddaaar cddaadaaaar cddaadaaadr cddaadaaar cddaadaadar cddaadaaddr
cddaadaadr cddaadaar cddaadadaar cddaadadadr cddaadadar cddaadaddar cddaadadddr
cddaadaddr cddaadadr cddaadar cddaaddaaar cddaaddaadr cddaaddaar cddaaddadar cddaaddaddr
cddaaddadr cddaaddar cddaadddaar cddaadddadr cddaadddar cddaaddddar cddaadddddr
cddaaddddr cddaadddr cddaaddr cddaadr cddaar cddadaaaaar cddadaaaadr cddadaaaar
cddadaaadar cddadaaaddr cddadaaadr cddadaaar cddadaadaar cddadaadadr cddadaadar
cddadaaddar cddadaadddr cddadaaddr cddadaadr cddadaar cddadadaaar cddadadaadr cddadadaar
cddadadadar cddadadaddr cddadadadr cddadadar cddadaddaar cddadaddadr cddadaddar
cddadadddar cddadaddddr cddadadddr cddadaddr cddadadr cddadar cddaddaaaar cddaddaaadr
cddaddaaar cddaddaadar cddaddaaddr cddaddaadr cddaddaar cddaddadaar cddaddadadr
cddaddadar cddaddaddar cddaddadddr cddaddaddr cddaddadr cddaddar cddadddaaar cddadddaadr
cddadddaar cddadddadar cddadddaddr cddadddadr cddadddar cddaddddaar cddaddddadr
cddaddddar cddadddddar cddaddddddr cddadddddr cddaddddr cddadddr cddaddr cddadr
cddar cdddaaaaaar cdddaaaaadr cdddaaaaar cdddaaaadar cdddaaaaddr cdddaaaadr cdddaaaar
cdddaaadaar cdddaaadadr cdddaaadar cdddaaaddar cdddaaadddr cdddaaaddr cdddaaadr
cdddaaar cdddaadaaar cdddaadaadr cdddaadaar cdddaadadar cdddaadaddr cdddaadadr cdddaadar
cdddaaddaar cdddaaddadr cdddaaddar cdddaadddar cdddaaddddr cdddaadddr cdddaaddr
cdddaadr cdddaar cdddadaaaar cdddadaaadr cdddadaaar cdddadaadar cdddadaaddr cdddadaadr
cdddadaar cdddadadaar cdddadadadr cdddadadar cdddadaddar cdddadadddr cdddadaddr
cdddadadr cdddadar cdddaddaaar cdddaddaadr cdddaddaar cdddaddadar cdddaddaddr cdddaddadr
cdddaddar cdddadddaar cdddadddadr cdddadddar cdddaddddar cdddadddddr cdddaddddr
cdddadddr cdddaddr cdddadr cdddar cddddaaaaar cddddaaaadr cddddaaaar cddddaaadar
cddddaaaddr cddddaaadr cddddaaar cddddaadaar cddddaadadr cddddaadar cddddaaddar
cddddaadddr cddddaaddr cddddaadr cddddaar cddddadaaar cddddadaadr cddddadaar cddddadadar
cddddadaddr cddddadadr cddddadar cddddaddaar cddddaddadr cddddaddar cddddadddar
cddddaddddr cddddadddr cddddaddr cddddadr cddddar cdddddaaaar cdddddaaadr cdddddaaar
cdddddaadar cdddddaaddr cdddddaadr cdddddaar cdddddadaar cdddddadadr cdddddadar
cdddddaddar cdddddadddr cdddddaddr cdddddadr cdddddar cddddddaaar cddddddaadr cddddddaar
cddddddadar cddddddaddr cddddddadr cddddddar cdddddddaar cdddddddadr cdddddddar
cddddddddar cdddddddddr cddddddddr cdddddddr cddddddr cdddddr cddddr cdddr cddr

Some useful tools there – surely some of these functions would be proud to appear in any Common Lisp program? How about the stretch-limo caaaaaaaaar, for one (“My god, it’s full of cars”)? Then there’s cadadar – north of the USA, if you have a cold. A few are useful in other ways, too: cdddddddddr provides excellent tonguing practice for woodwind players, especially the bassoonists among you.

By the way, for compatibility with Common Lisp, it’s not necessary to go all the way up 1022. Call (cdadderize 14) to give you:

(caaar caadr caar cadar caddr cadr car cdaar cdadr cdar cddar cdddr cddr cdr)

whereas 30 gives you everything up to cddddr.

To be honest, I can’t see myself using these very much. Well, OK: I will never use these. But I like the idea that the ever-adaptable Lisp was once written for vacuum-tubes and can still run like the wind on my iMac.


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