Why don't people like lisp?

[Brian Kelley]

Tayss wrote:

> http://groups.google.com/groups?hl=en&lr=&ie=UTF-8&oe=UTF-8&safe=off&selm=3F1F5297.15D768EF%40alcyone.com
> Erik Max Francis explains that expecting the system to close files
> leads to brittle code.  It's not safe or guaranteed.
> 
> After learning Python, people write this bug for months, until they
> see some article or usenet post with the try/finally idiom.  

Some more than most.  Interestingly, I write proxies that close 
resources on failure but tend to let files do what they want.

> Now, I love Python, but this really is a case where lots of people
> write lots of potentially hard-to-reproduce bugs because the language
> suddenly stopped holding their hands.  This is where it really hurts
> Python to make the tradeoff against having macros.  The tradeoff may
> be worth it, but ouch!

I choose a bad example on abusing the C-implementation.  The main thrust 
of my argument is that you don't need macros in this case, i.e. there 
can be situations with very little tradeoff.

class SafeFileWrapper:
    def __init__(self, f):
        self.f = f

    def write(self, data):
        try: self.f.write(data)
        except:
         self.f.close()
	self.f = None
         raise

     def close():
         if self.f:
            self.f.close()
    ...

Now the usage is:

f = SafeFileWrapper(open(...))
print >> f, "A couple of lines"
f.close()

So now I just grep through my code for open and replace it with 
SafeFileWrapper(open...) and all is well again.

I still have to explicitly close the file though when I am done with it, 
unless I don't care if it is open through the application run.  But at 
least I am guaranteed that the file is closed either when I tell it to 
or on an error.

Brian Kelley