On 3/10/06, Alan Gauld <[EMAIL PROTECTED]> wrote:
Someone writing a named function is less likely to feel constrained to do an obscure "one-liner".
This, is clear, and the kind of thinking that, imho, writing an actual function promotes. The other useful thing with this is: if you give it real name instead of an anonymous, meaningless f, you can actually call the function from other modules, or reuse it in other programs. Meaningful naming also enhances readability. How much did we all have to go through to figure out that this was a factorial function. What if, instead, it had actually been given a real name, like, say "factor"... No need to work through the complex code just to figure out what it was for.
Precisely. They are used as shortcuts and usually are far too clever by half. I've seen a few people like you who use them clearly; unfortunately, that's not the norm.
Well - the nice thing is that we both get to be right! ;-) And I think it's useful to get the pros and cons out occasionally where newbies can see that we don't all agree on everything, but that we can disagree politely and still be helpful.
Anna
>> Could you please explain this code?.
>>
>> f = lambda n: n-1 + abs(n-1) and f(n-1)*n or 1
>
> This is why lambdas are evil.
It's not the lambda thats evil its the need in Python to limit
them to a single _expression_.
If we write
def f(n):
return n-1 + abs(n-1) and f(n-1)*n or 1
its just as obscure.
Someone writing a named function is less likely to feel constrained to do an obscure "one-liner".
if we write
def f(n)
if not ((n-1) + abs(n-1)):
return f(n-1) * n
else return 1
it gets a little clearer. And the only time the if _expression_
is false is when n is zero or 1 so for the last time:
def f(n)
if n >1:
return f(n-1) * n
else:
return 1
This, is clear, and the kind of thinking that, imho, writing an actual function promotes. The other useful thing with this is: if you give it real name instead of an anonymous, meaningless f, you can actually call the function from other modules, or reuse it in other programs. Meaningful naming also enhances readability. How much did we all have to go through to figure out that this was a factorial function. What if, instead, it had actually been given a real name, like, say "factor"... No need to work through the complex code just to figure out what it was for.
In fact its the factorial function in very strange disguise!
If we could write the lambda as
f = lambda n:
if n>1:
return f(n-1) * n
else return 1
is it so much more complex?
> Officially, they are for creating "anonymous functions";
> usually they only succeed in creating obscure unreadable drek.
Unfortunately that's true. But as a concept they are a fundamental
part of computing science and its hard to understamnd higher order
programming or explore predicate calculus without them
They are also of course very useful as shortcuts but thats usually
where the cryptic code comes in.
Precisely. They are used as shortcuts and usually are far too clever by half. I've seen a few people like you who use them clearly; unfortunately, that's not the norm.
> In My Humble Opinion.
And in mine, of course :-)
Well - the nice thing is that we both get to be right! ;-) And I think it's useful to get the pros and cons out occasionally where newbies can see that we don't all agree on everything, but that we can disagree politely and still be helpful.
Anna
_______________________________________________ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
