On Fri, 09 Dec 2011 09:25:34 -0500, Regan Heath <[email protected]>
wrote:
On Fri, 09 Dec 2011 13:42:34 -0000, Timon Gehr <[email protected]> wrote:
On 12/09/2011 02:28 PM, Regan Heath wrote:
On Fri, 09 Dec 2011 13:15:47 -0000, Timon Gehr <[email protected]>
wrote:
On 12/09/2011 01:36 PM, Regan Heath wrote:
4)
if (std.ascii.toLower(p.front) == 'n' &&
(p.popFront(), std.ascii.toLower(p.front) == 'f') &&
(p.popFront(), p.empty))
'if' statements with side effects are yuck. I prefer the check for
error
and bail style but you could use multiple layers of 'if' instead..
if (std.ascii.toLower(p.front) != 'n') //error handling
p.popFront();
if (std.ascii.toLower(p.front) != 'f') //error handling
p.popFront();
if (!p.empty) //error handling
Your '//error handling' shortcut hides relevant information.
What information? With context I could be more specific about what to
do
for each/all.
You can always grep the Phobos source to get context. Basically, you
are suggesting to replace the comma operator with gotos:
case 'i': case 'I':
p.popFront();
if (std.ascii.toLower(p.front) == 'n' &&
(p.popFront(), std.ascii.toLower(p.front) == 'f') &&
(p.popFront(), p.empty))
{
// 'inf'
return sign ? -Target.infinity : Target.infinity;
}
goto default;
default: {}
}
If using 'goto' is the 'correct' agreed upon style for phobos then,
yes. It's not my personal preference however and I'd probably refactor
it further if it was my own code.
goto in this case is acceptable. It's a goto case statement, which
technically should be required for fall-through.
5)
enforce((p.popFront(), !p.empty && std.ascii.toUpper(p.front) ==
'A')
&& (p.popFront(), !p.empty && std.ascii.toUpper(p.front) == 'N'),
new ConvException("error converting input to floating point"));
This is blatant enforce abuse IMO..
p.popFront();
if(p.empty || std.ascii.toUpper(p.front) != 'A'))
throw new ConvException("error converting input to floating point"));
p.popFront();
if(p.empty || std.ascii.toUpper(p.front) != 'N'))
throw new ConvException("error converting input to floating point"));
This is blatant code duplication.
Of the throw line? Sure, and you can re-write with nested 'if' if you
prefer. I prefer the code duplication tho.
Code duplication is very error prone. Furthermore I never ever want to
duplicate _error handling_ code. That just clutters up the generated
machine code if the compiler does not manage to reverse engineer and
generate the proper solution.
I can't comment on the machine code aspect. I don't find this
particular duplication error prone, but if you do you can use the nested
if that I've already mentioned.
This case is a perfect example of what is right and wrong with the comma
operator.
With the comma operator, the single statement avoids code duplication,
which is good for maintenance. However, it's extremely hard to see what's
going on. Timon, please accept that you may be one of the few who reads
that statement and sees perfectly what's happening, I needed to read
Regan's version to understand what it does without hurting my head too
much.
My opinion? I think it's better written like this:
p.popFront();
bool bad = void;
if(!(bad = p.empty || std.ascii.toUpper(p.front) != 'A'))
{
p.popFront();
bad = p.empty || std.ascii.toUpper(p.front) != 'N';
}
if(bad)
throw new ConvException("error converting input to floating point");
And I'd probably reread it again, and throw in some comments to help me
remember what the f*** I was doing :)
I don't see a smaller solution, or one that doesn't use a temporary,
without using the comma operator or duplicating the throw/enforce call.
-Steve
