merits of Lisp vs Python

[André Thieme]

Paul Rubin schrieb:
 > André Thieme <address.good.until.2006.dec.22 at justmail.de> writes:
 >> and the Lisp version has only 9:
 >> nth, 1+, truncate, signum, num, list, pos, zero, neg
 >
 > Oh come on, you have to count the parentheses too.

We could define hundreds of way how to count tokens.
But see the program as a tree:

                      nth
                     /   \
                   /       \
                 /           \
                1+          list
                |           / | \
                |         /   |   \
            truncate    pos  zero  neg
                |
                |
             signum
                |
                |
               num

And I didn't count the indentation level and \n in Python code.
Why should I? They are editor commands.


 > Anyway, token count doesn't mean much, you have to instead go by the
 > user's cognitive effort in dealing with the prefix notation etc.,

How complicated ss it to say "cmp(a, b)" compared to  "a cmp b"?
After a few days writing Lisp code your brain specializes on that
style. Arabian countries write from right to left. They seem to have
no problem to use what they know.
I admit that I am used to write +, -, * and / infix, because I were
trained in that thinking since day 1 in school.
In our example program there was only 1+ compared to ".. + 1" which
looks "alien" to untrained people.
If a program uses extensive math we can get syntax for Lisp that is
even more pleasant to read than Pythons:
17a + x³-x²



 > which isn't purely a matter of token count.  And if (+ 2 3) were
 > really as easy to read as 2+3, mathematics would have been written
 > that way all along.

Mathmaticians invented prefix notation and they use it regularily.
They inventey operators that wrap around their arguments, as one can
see here: http://www.mathe-trainer.com/formel/?SN=&t=1

Or think of indices, etc.



 >> TypeError: 'str' object is not callable
 >> I don't know how I can fix that. Maybe you could tell me.
 >
 >>>> lazy_nif(0, lambda: "p", lambda: "z", lambda: "n")

Yes, that works. And that's why I wanted to make it a macro.
Now you are essentially doing what I did in my first Lisp version.
While this works it is farer away from what we think.

(nif 0 "p" "z" "n")
(nif 0 #'p #'z #'n)
are exactly what one thinks.
For this reason "if" is implemented as a keyword in Python.
It allows you to give code as a block instead of embedding it into
a lambda or a def (which even needs a name).


And we might go further (again with an easy Graham example).
See this typical pattern:

result = timeConsumingCalculation()
if result:
   use(result)

We need this ugly temporary variable result to refer to it.
If we could use the anaphor[1] "it" that could make situations like
these more clean.

Imagine Python would have an "anaphoric if", "aif". Then:

aif timeConsumingCalculation():
   use(it)

Many Lispers might have this as a macro in their toolbox after some
time of coding or after reading Graham.
A short three-liner in Lisp and I can really say:

(aif (timeConsumingCalculation)
      (use it))

How would you solve this in Python?
You could embed it inside a lambda and must somehow make the
variable "it" visible in it, because in the context of aif this
"it" gets bound to the result.



 >>> All Haskell evaluation is automatically lazy, so no lambdas etc. 
needed.
 >> Yes, that was what I already supposed.
 >> Do you also know how I can "deactivate" lazyness?
 >
 > There's a Haskell builtin called 'seq' which forces evaluation but
 > again I'm not sure precisely how to apply it here.

I wouldn't wonder if there was an operator like "seq" to do that.
So in some languages that support functional programming one needs to do
extra work to get lazyness, while in Haskell one gets extra work if one
doesn't want it. But maybe someone can correct me here.
In Lisp one could build some features to get lazyness as well.


[1] http://en.wikipedia.org/wiki/Anaphora_%28linguistics%29

I hope this posting was not sent two times. I just sent it but it didn't
appear in my list after reloading.


André
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