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Re: Python vs Lisp (followups to -tangents)
From: |
Random832 |
Subject: |
Re: Python vs Lisp (followups to -tangents) |
Date: |
Thu, 10 Dec 2015 22:31:49 +0000 (UTC) |
User-agent: |
slrn/pre1.0.3-7 (Linux) |
On 2015-12-10, Sam Steingold <address@hidden> wrote:
> This is false.
> Nested lists are certainly printed readably:
What I meant by "not structure-preserving" is that the output is
the same, ((1 2) (1 2)), for these lists:
(let ((x '((1 2) (1 2)))) (eq (car x) (cadr x))) ==> nil
(let* ((a '(1 2)) (x `(,a ,a))) (eq (car x) (cadr x))) ==> t
(let ((x (read "((1 2) (1 2))"))) (eq (car x) (cadr x))) ==> nil
(Or for that matter, let*
((b '(2)) (x (list (cons 1 b) (cons 1 b))))...)
> True, but irrelevant.
>An important feature is missing: repr is not defined for classes
> automatically.
Sure it is. It's just defined to the same kind of useless value
that Lisp has for buffers and subroutines.
>> Python's 'eval'/'exec' normally evaluates code directly from a
>> string, skipping the need for 'read' entirely.
>
> A string is too unstructured.
>
>> However, if desired, the 'ast' module provides a rich framework for
>> working with expression trees - the only difference is that they're
>> built from class-based objects instead of just being a list of
>> lists/symbols/literals.
>
> These class-based objects cannot be printed readably (IIUC).
It's unfortunate that this is not their repr output, but the
ast.dump function provides this:
>>> ast.dump(ast.parse("1 + 1"))
'Module(body=[Expr(value=BinOp(left=Num(n=1), op=Add(), right=Num(n=1)))])'
>>> eval(ast.dump(ast.parse("1 + 1")), ast.__dict__)
<_ast.Module object at 0x7fcd79b24908>
> The point Richard is making is that Python lacks macros, i.e., you
> cannot easily write code which writes code.
> You have to either operate at the level of strings (which is hard to get
> right) or at the level of AST (which is even harder).
I don't see how operating at the level of AST is harder than
operating at the level of lists (backquote operates above the
level of lists; it automatically searches the code you give it
for placeholders to substitute values in. It probably wouldn't
be hard to write an equivalent in Python.)
> Even more succinctly, in Lisp data and code are the same: lists of
> lists, symbols, strings &c.
> In Python, data is (mostly) strings and code is AST.
I guess I don't see how being a little rough around the edges or
not working exactly the same way is the same thing as missing
the essential features entirely.
And this really isn't a valid objection to the claim being
discussed, which is that Python is similar to a hypothetical
M-expression lisp.
- Re: First draft of the Emacs website, (continued)
- Re: First draft of the Emacs website, Spencer Boucher, 2015/12/08
- Re: First draft of the Emacs website, David Kastrup, 2015/12/08
- Re: First draft of the Emacs website, Marcin Borkowski, 2015/12/08
- RE: First draft of the Emacs website, Drew Adams, 2015/12/08
- RE: First draft of the Emacs website, Drew Adams, 2015/12/08
- Re: First draft of the Emacs website, Marcin Borkowski, 2015/12/09
- Re: First draft of the Emacs website, Richard Stallman, 2015/12/10
- Re: First draft of the Emacs website, David Kastrup, 2015/12/10
- Re: First draft of the Emacs website, Richard Stallman, 2015/12/10
- Message not available
- Re: Python vs Lisp (followups to -tangents), Sam Steingold, 2015/12/10
- Re: Python vs Lisp (followups to -tangents),
Random832 <=
- Re: Python vs Lisp (followups to -tangents), Sam Steingold, 2015/12/16
- Re: Python vs Lisp (followups to -tangents), Christopher Allan Webber, 2015/12/16
- Re: First draft of the Emacs website, Richard Stallman, 2015/12/09
- Re: First draft of the Emacs website, David Kastrup, 2015/12/04
- Re: First draft of the Emacs website, Eli Zaretskii, 2015/12/04
- Re: First draft of the Emacs website, David Kastrup, 2015/12/04
- Re: First draft of the Emacs website, Eli Zaretskii, 2015/12/04
- Re: First draft of the Emacs website, Nicolas Petton, 2015/12/04
- Re: First draft of the Emacs website, David Kastrup, 2015/12/04
- Re: First draft of the Emacs website, Eli Zaretskii, 2015/12/04