Poll on Eval in Ruby

Ruby
1

I am Lisp programmer and I write an article on
issues as macros, fexprs and eval. I want to
compare opinion of Ruby and Lisp programmers on eval.
Some readers might think that such post constitute
spam on Ruby newsgroup, but I believe that resulting
information will not be completely devoid of value

  • even for Ruby community.

If you want to contribute few seconds, the poll is
on my blog, on the top of the right column.

http://kazimirmajorinc.blogspot.com

Thanks,

2

On 9.10.2009 18:43, David M. wrote:

So… I avoid languages that don’t have eval. But I avoid using eval in the
languages I use. Does that make sense?

It has, David. I think it is, lets say,
developed form of “useful but overused”
opinion.

3

On Thursday 08 October 2009 08:15:06 am Kazimir Majorinc wrote:

I want to
compare opinion of Ruby and Lisp programmers on eval.
…
If you want to contribute few seconds, the poll is
on my blog, on the top of the right column.

http://kazimirmajorinc.blogspot.com

There wasn’t an option for “Absolutely essential for the one time out of
a
billion you actually need it. Otherwise, avoid it entirely.”

I can’t remember the last time I used eval directly in Ruby, and I’ve
seen it
maybe once or twice in library code. I’ve also seen it abused by people
who
really should know better. 90% of the time you find yourself reaching
for eval,
you’re Doing It Wrong. Another 9% of the time, you’re working around a
missing
language feature, and it’d be better to fix that feature, or at least
bury your
use of eval deep in a library.

But there was the time I used Javascript on HD-DVD, which had many
limitations, including not having eval. And many of its other
limitations
could’ve been worked around if there had been an eval. A simple example:
Downloading and executing code was complex and often disruptive – eval
would’ve made it trivial.

So… I avoid languages that don’t have eval. But I avoid using eval in
the
languages I use. Does that make sense?

4

On Friday 09 October 2009 01:10:07 pm Kazimir Majorinc wrote:

On 9.10.2009 18:43, David M. wrote:

So… I avoid languages that don’t have eval. But I avoid using eval in
the languages I use. Does that make sense?

It has, David. I think it is, lets say,
developed form of “useful but overused”
opinion.

Well, except that I’m not making any statement about how people use it,
because I don’t know. The few examples I’ve found don’t point to any
sort of
systemic overuse – if there’s a language feature, someone has found a
way to
abuse it.

5

If you want to contribute few seconds, the poll is
on my blog, on the top of the right column.

Are we talking about

a = 'foo'
b = 'a + "bar"'
eval "'yummy ' + #{b} * 2"

or about

class A
    def initialize
        @x = "foo"
    end
end

A.new.instance_eval {@x}
6

On Sat, Oct 10, 2009 at 7:10 AM, lith [email protected] wrote:

class A
def initialize
@x = “foo”
end
end

A.new.instance_eval {@x}

I thought we were talking about all eval version (eval, instance_eval,
class_eval, etc) so I answered the one that was “has it’s place” or
something like that.

If we are talking exclusively about pure eval, I agree with David, I
almost never use it.

Jesus.

7

Hi –

On Sat, 10 Oct 2009, Jesús Gabriel y Galán wrote:

or about
class_eval, etc) so I answered the one that was “has it’s place” or
something like that.

If we are talking exclusively about pure eval, I agree with David, I
almost never use it.

I make a distinction between *eval’ing a string, which always carries
all the dangers of regular eval, and the block forms of instance_eval
and class/module_eval, which are very different techniques and don’t
have the same dangers.

David

–
The Ruby training with D. Black, G. Brown, J.McAnally
Compleat Jan 22-23, 2010, Tampa, FL
Rubyist http://www.thecompleatrubyist.com

David A. Black/Ruby Power and Light, LLC (http://www.rubypal.com)

8

On Oct 10, 2009, at 9:55 AM, David A. Black wrote:

I make a distinction between *eval’ing a string, which always carries
all the dangers of regular eval…

I’m just not sure eval()ing a String or regular ole eval() are alway
dangerous. I wrote about that a little on my blog recently:

http://blog.grayproductions.net/articles/eval_isnt_quite_pure_evil

James Edward G. II

9

Hi –

On Sun, 11 Oct 2009, James Edward G. II wrote:

On Oct 10, 2009, at 9:55 AM, David A. Black wrote:

I make a distinction between *eval’ing a string, which always carries
all the dangers of regular eval…

I’m just not sure eval()ing a String or regular ole eval() are alway
dangerous. I wrote about that a little on my blog recently:

I don’t think so either; I only mean that all the string eval’ing
techniques are essentially the same as each other, while the block
ones are very different.

David

–
The Ruby training with D. Black, G. Brown, J.McAnally
Compleat Jan 22-23, 2010, Tampa, FL
Rubyist http://www.thecompleatrubyist.com

David A. Black/Ruby Power and Light, LLC (http://www.rubypal.com)

10

THE RESULTS OF THE POLLS
========================

. Lisp Python Ruby

Eval is evil,
harmful or at
least unnecessary 2 (4.9%) 7 (21.9%) 0 (0.0%)

Eval is useful
but overused 11 (26.8%) 6 (18.8%) 9 (29.0%)

Eval has just the
right place 16 (39.0%) 10 (31.3%) 19 (61.3%)

Eval is useful
but neglected 3 (7.3%) 4 (12.5%) 1 (3.2%)