robert-van-engelen / lisp Goto Github PK

I tried this: nested define:

rs.lisp:

; if these defines are not nested, it works.
; (define take (lambda (n seq) (if (<= n 0) (quote ()) (cons (car seq) (take (- n 1) (cdr seq))))))
; (define drop (lambda (n seq) (if (<= n 0) seq (drop (- n 1) (cdr seq)))))
; (define mid (lambda (seq) (/ (length seq) 2)))

(define combine (lambda (f)
        (lambda (x y)
          (if (null? x) (quote ())
              (f (list (car x) (car y))
                 ((combine f) (cdr x) (cdr y)))))))

; but not inside:
(define riff-shuffle (lambda (deck) (begin
      (define take (lambda (n seq) (if (<= n 0) (quote ()) (cons (car seq) (take (- n 1) (cdr seq))))))
      (define drop (lambda (n seq) (if (<= n 0) seq (drop (- n 1) (cdr seq)))))
      (define mid (lambda (seq) (/ (length seq) 2)))
      ((combine append) (take (mid deck) deck) (drop (mid deck) deck)))))

(riff-shuffle (list 1 2 3 4 5 6 7 8))

unbound take ERR 3 unbound symbol:

6322+1929>(load "rs.lisp")
(load "rs.lisp")
combine
riff-shuffle
unbound take ERR 3 unbound symbol

6024+1921>(riff-shuffle (list 1 2 3 4 5 6 7 8))
unbound take ERR 3 unbound symbol

the correct output should be:

> (load "rs.lisp")
> (riff-shuffle (list 1 2 3 4 5 6 7 8))
(1 5 2 6 3 7 4 8)

Is there any reason why the following macro raises an error:
(define ++ (macro (x) (list 'setq x (list '+ x 1))))
It is ment to act like the C function '++'. The error text is: unbound symbol. The symbol appears to be the '+

I’ve encountered a problem leading to infinite recursion because the wrong ‘int read()’ function is being linked (silently) when using readline. I’ve verified this happens on two distinct systems (Redhat Linux, Alpine Linux). The solution is to rename the read() symbol in lisp.c to lread() or anything other than read().

An interesting way to specify a while loop is the following:

(define while (lambda (body . args)
(apply body body args)))
(while (lambda (loop i)
(if (not (eq? i 0))
(begin
(print i)
(loop loop (- i 1)))
'done)) 5)

It should print '54321done'. In your lisp implementation all needed functions are available, except 'apply'. Actually this function is used in a lot of other clever lisp examples, and it cannot be written as a macro. Do you think you can create it in your program?

Hello,

What a wonderful lisp implementation, good job. Can you please add at least one example of how to call a new C defined function from lisp? (I am new to Lisp so maybe I missed it in the readme).

As it is a good candidate for many embedded platforms (microcontrollers), maybe it could be worth to wrap the (f)printf functions so that theses ones are defined on the host side rather than in the library.

Thank you!

(cond (() 42)) errors with ERR 1 not a pair, whereas I would expect it to evaluate to ().

(if () 42) evaluates to (), as I would expect.

I'm not sure if this is a bug in cond or if I'm misunderstanding how it's supposed to work.