bearophile wrote:
Few comments of mine about this, written by Andrei:
http://lists.puremagic.com/pipermail/phobos/2010-August/001757.html
* Generally the prevalent Phobos (and I hope D) style is to declare
local values as late as possible.
Good.
Defining variables at the top of the function/method is positive because it
makes the code tidy and it's easy to see in a moment all variables used
(Pascal-like languages nearly enforce this). But defining them as close as
possible to their usage point has usually bigger advantages that I don't list
here. But as usual all rules need to be used in a flexible way.
On the other hand global variables/constants are global both in scope and their
definition order doesn't matter, so I think that putting them all at the top of
the module is better.
* In D, use of auto is recommended unless you want to make a
specific point by mentioning the type.
This is where I don't agree. "auto" is very handy. When you have complex types
coming out of lazy map, filter, etc, auto becomes very important, writing code becomes
simpler.
On the other hand code needs to be read too, sometimes by people that have not written
it. In this case seeing the actual types used is often better. So using "auto"
everywhere makes the code reading harder: if you aren't using an IDE that tells you
types, you sometimes need to follow the flux of the various calls until you find what is
the type, or sometimes you need to add temporary writeln(typeof(x).stringof); inside the
code to see what type it is. This problem is common in dynamic languages.
So 'auto' can be abused, online you can find plenty of discussions about
disadvantages of 'auto' in C++0x and 'var' in C#. I like the D 'auto' and I use
it, but in my opinion it's bad to use it everywhere and to encourage too much
its usage. D lacks the flexibility of a dynamic language, so it's not positive
to hide too much the types of variables from the person that reads the code.
[citation needed]
A cursory googling didn't find many discussions.
Andrei
