Posted by veqq 12 hours ago
(defun add (a &rest b)
(if (null b)
a
(+ a (eval (cons '+ b)))))
(defun add (a &rest b)
(if (endp b) a
(apply #'add (+ a (first b)) (rest b)))) (defparameter *a* '(1 2 3))
(setf (car *a*) 3)
All major Common Lisps support tail call optimization with proper declarations, with the exception of ABCL because it runs on the JVM.
And those declarations are all identical or almost identical, so it's easy to write an implementation-specific macro to guarantee TCO if you need to do so.
Some algorithms are easiest to express and read with looping constructs. For those algorithms, use looping constructs. Other algorithms are easiest to express and read with recursion. For those, use recursion. You shouldn't be afraid of recursion just because ANSI doesn't say TCO is guaranteed. You should be afraid of it if your code needs to run on ABCL, but otherwise, recur on.
I prefer to write my state-machines as transitioning with tail-calls, and I do get called for it. It's relatively easy to switch something written in that manner to using a loop with a trampoline, so I do so when my collaborators request it.
Even with SBCL, for example, it doesn't have tail-call optimisation for all architectures at all optimisation levels.
- why nothing on the "compiler" line? Everytime you load a snippet or a file with SBCL, it compiles it (to machine code). There's also compile-file.
- interpreter: likewise, all code is compiled by default with SBCL, not interpreted, even in the REPL. To use the interpreter, we must do this: https://github.com/lisp-tips/lisp-tips/issues/52
- command line program: the racket cell shows the use of -e (eval), the same can be done with any CL implementation.
- since the string split line introduces cl-ppcre, one could mention cl-str :D (plug) (much terser join, trim, concat etc)
- ah ok, for dates and times, flattening a list, hash-table literals… we need more libraries.
- more files operations: https://lispcookbook.github.io/cl-cookbook/files.html
- emacs buffers: now compare with Lem buffers 8-)
- posix-getenv: I'd rather use uiop:getenv (comes in implementations).
- uiop:*command-line-arguments*
- exit: uiop:quit
- uiop:run-program (sync) / launch-program (async)
- java interop: with LispWorks or ABCL (or other libraries)
my 2c
local-time has its limits (e.g. Gregorian only), but it does everything listed in this chart
> flattening a list
What? Isn't this[1] just fine (<s>)
> hash-table literals…
Since the chart is sbcl specific, this ugly mess would technically count; a more portable (but longer) version could be made similarly using #.:
#.(SB-IMPL::%STUFF-HASH-TABLE (MAKE-HASH-TABLE :TEST 'EQUAL) '((:X . :Y)))
I've had good luck with .net/java interop using FOIL (written by Rich Hickey prior to Clojure).
1:
CL-USER> (let* ((result (cons nil nil))
(tail result))
(subst-if t
(constantly nil)
'(a ((b(c d)) e) f)
:key (lambda (x)
(when (and x (atom x)) (setf (cdr tail) (cons x nil)
tail (cdr tail)))))
(cdr result)) (documentation 'documentation 'function)
"Return the documentation string of Doc-Type for X, or NIL if none
exists.
System doc-types are VARIABLE, FUNCTION, STRUCTURE, TYPE, SETF, and T.
Also http://rosettacode.org for computer tasks implemented in many computer languages to allow you compare syntax and code. (loop for file across "ABCDEFGH"
nconc (loop for rank from 1 to 9
collect (format nil "~C~D" file rank)))Something I've been meaning to do is try putting together a cross-lisp package manager -- if only because it'd be fun. Maybe it would favor code that could be readily run or eval'd or maybe with some sort of clj/cljs type dynamic dispatch for anything implementation specific.