Re: Curious compiler warning
On 01/11/2012 10:03 AM, Patricia Shanahan wrote:
On 1/11/2012 6:58 AM, Lew wrote:
...
"Readability" is such a subjective term. Someone who knows C, C++, C#,
Java or certain other languages might find 'x[i++] = y[j++]" perfectly
readable. Someone not familiar with these programming languages might not.
I am familiar with C and C++. In the case of C, I've led a compiler
implementation project. I fully understand that expression.
It seems less obvious to me than it would written out as three
statements. Just as I like methods with a single clear purpose, I prefer
statements that have a single clear purpose such as "copy an element
from y to x", or "increment i".
Good point.
If your observation that such expressions has any evidence to back it up
it's a good argument for something. Maybe not for changing the potency
of the auto-inc/decrement operator but for hiring better-trained
programmers, but for something. Assuming the evidence sustains the
observation.
If you have a hard time understanding that expression and you call
yourself a Java programmer, there's a disconnect.
Fortunately, I don't care about being a Java programmer, or a C
programmer, or any other qualified sort of programmer. I'm just a
programmer. For my purposes, writing simple, obvious code in whatever
language I happen to be using is far more important than showing off my
understanding of the JLS.
The JLS itself agrees with me on this: "It is recommended that code not
rely crucially on this specification. Code is usually clearer when each
expression contains at most one side effect, as its outermost operation,
and when code does not depend on exactly which exception arises as a
consequence of the left-to-right evaluation of expressions."
[http://java.sun.com/docs/books/jls/third_edition/html/expressions.html#15.7]
The block:
{
x[i] = y[i];
i++;
j++;
}
follows that recommendation. Squishing all three side effects into one
statement does not.
I would go against a JLS recommendation about how to use the language
only if I had a strong positive reason to do so. That is especially the
case when it is arguing for simplicity, which I would prefer anyway.
Well, they're not so much talking about how to use the language as about
programming style generally, so it's not normative, though it is good advice.
I just don't happen personally to agree that 'stuff[++index]' is all that
difficult to comprehend or all that dangerous to use, but I'm also no opponent
of verbosity in service of clarity. So my question about why the
autodecrement was on a separate line has been fully and usefully answered, and
I encourage everyone to do so.
But if you aren't using the old value, please use the prefix form of the operator.
That autodecrement was used at all in the OP's example is still open to criticism.
--
Lew
Honi soit qui mal y pense.
http://upload.wikimedia.org/wikipedia/commons/c/cf/Friz.jpg