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Lisp from Nothing, Second Edition

t3x.org

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Re: Lisp from Nothing, Second Edition

#3

Post by gritzko »

nils-m-holm wrote: post #2

Second edition, with a new chapter on lambda calculus.

Thanks. I recently had to reinvent LISP to script my CRDT database. That was not much work, because I already had the notation (I use RDX, a JSON superset with CRDT types). Still, I stumbled at the idiosyncratic LISP bracketing. Luckily, RDX allows for different tuple notations. So, I styled it to look less alien to a curly-braced developer. Like this https://github.com/gritzko/go-rdx/blob/main/test/13-getput.j...

For example, print change-dir make-dir; is equivalent to (print (change-dir (make-dir) ) ) in the old money. I wonder if I am reinventing too much here.

Did LISPers try to get rid of the brackets in the past?

Re: Lisp from Nothing, Second Edition

#4

Post by AlexeyBrin »

gritzko wrote: post #3
nils-m-holm wrote: post #2

Second edition, with a new chapter on lambda calculus.

Thanks. I recently had to reinvent LISP to script my CRDT database. That was not much work, because I already had the notation (I use RDX, a JSON superset with CRDT types). Still, I stumbled at the idiosyncratic LISP bracketing. Luckily, RDX allows for different tuple notations. So, I styled it to look less alien to a curly-braced developer. Like this https://github.com/gritzko/go-rdx/blob/main/test/13-getput.j... Fo…

If you don't get an answer here, try to contact the author directly through his website, he is pretty responsive.

Re: Lisp from Nothing, Second Edition

#5

Post by drob518 »

gritzko wrote: post #3
nils-m-holm wrote: post #2

Second edition, with a new chapter on lambda calculus.

Thanks. I recently had to reinvent LISP to script my CRDT database. That was not much work, because I already had the notation (I use RDX, a JSON superset with CRDT types). Still, I stumbled at the idiosyncratic LISP bracketing. Luckily, RDX allows for different tuple notations. So, I styled it to look less alien to a curly-braced developer. Like this https://github.com/gritzko/go-rdx/blob/main/test/13-getput.j... Fo…

There have been many attempts to get rid of sexprs in favor of a “better” syntax. Even John McCarthy, the inventor (discoverer?) of Lisp had plans for an “M-expression” syntax to replace “S-expressions.” It never happened. The secret is that Lispers actually view sexprs as an advantage, not something to be worked around. Once you discover symbolic editing and code manipulation based on sexprs, you’ll never go back to weak line editing. That said, some Lisp dialects (e.g. Clojure and Racket) have embraced other symbols like square and curly brackets to keep the code more terse overall and optically break up longer runs of parentheses.

Probably the best example of a “Lisp without parentheses” is Dylan. Originally, Dylan was developed as a more traditional Lisp with sexprs, but they came up with a non-sexr “surface syntax” before launching it to avoid scaring the public.

Re: Lisp from Nothing, Second Edition

#6

Post by bryanlarsen »

gritzko wrote: post #3
nils-m-holm wrote: post #2

Second edition, with a new chapter on lambda calculus.

Thanks. I recently had to reinvent LISP to script my CRDT database. That was not much work, because I already had the notation (I use RDX, a JSON superset with CRDT types). Still, I stumbled at the idiosyncratic LISP bracketing. Luckily, RDX allows for different tuple notations. So, I styled it to look less alien to a curly-braced developer. Like this https://github.com/gritzko/go-rdx/blob/main/test/13-getput.j... Fo…

Many times. A google for "sweet expressions lisp" will give you a bunch of implementations and opinions.

Re: Lisp from Nothing, Second Edition

#8

Post by gritzko »

bryanlarsen wrote: post #6
gritzko wrote: post #3

Earlier quoted context omitted.

Thanks. I recently had to reinvent LISP to script my CRDT database. That was not much work, because I already had the notation (I use RDX, a JSON superset with CRDT types). Still, I stumbled at the idiosyncratic LISP bracketing. Luckily, RDX allows for different tuple notations. So, I styled it to look less alien to a curly-braced developer. Like this https://github.com/gritzko/go-rdx/blob/main/test/13-getput.j... Fo…

Many times. A google for "sweet expressions lisp" will give you a bunch of implementations and opinions.

Aha, thanks https://dwheeler.com/readable/

Re: Lisp from Nothing, Second Edition

#9

Post by tromp »

Looking at file church.scm from the provided zip file [1], I see the following functions used to construct lists:

    (define kons
      (lambda (x) (lambda (y) ((pair false) ((pair false) ((pair x) y))))))
    
    (define kar   (lambda (x) (first (second (second x)))))
    (define kdr   (lambda (x) (second (second (second x)))))
    
    (define nil   ((pair true) ((pair true) false)))
    (define null  first)
    
    (define atom  (lambda (x) (first (second x))))
That's 2 extra booleans per list element. While the one for recognizing atoms is probably necessary, the other one for recognizing nil is not:

    (define kons
      (lambda (x) (lambda (y) ((pair false) ((pair x) y)))))
    
    (define kar   (lambda (x) (first (second x))))
    (define kdr   (lambda (x) (second (second x))))
    
    (define nil ((pair true) false))
    (define null (lambda (x) (((second x) (lambda (a) (lambda (d) (lambda (z) false)))) true)))
    
    (define atom  (lambda (x) (first x)))
The use of null+car+cdr can usually be avoided by using a matching construct instead like

    (((second list) (lambda (a) (lambda (d) (lambda (z) deal_with_car_a_and_cdr_d ) deal_with_nil)
[1] https://t3x.org/lfn/church.zip

Re: Lisp from Nothing, Second Edition

#10

Post by [deleted] »

tromp wrote: post #9

Looking at file church.scm from the provided zip file [1], I see the following functions used to construct lists: (define kons (lambda (x) (lambda (y) ((pair false) ((pair false) ((pair x) y)))))) (define kar (lambda (x) (first (second (second x))))) (define kdr (lambda (x) (second (second (second x))))) (define nil ((pair true) ((pair true) false))) (define null first) (define atom (lambda (x) (first (second x)))) T…

[deleted]
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