philosophy : ! vs false

[Collin VanDyck]

I tried to search the usenet for the same question...

Well I would like to know which is the coding style that you prefer

boolean booleanValue=getABooleanValue();
if (!booleanValue) {
doSomething();
}

Or

boolean booleanValue=getABooleanValue();
if (booleanValue == false) {
doSomething();
}

Chirping in once more to say that I find the way that XSLT will allow
one to negate a boolean to be the most readable:

<xsl:if test="not($var='true')">

</xsl:if>

It would be nice if you could extend the JLS with macros, or some sort
of pre-processor that would let you use:

if (not(isValidXMLDocument))
{
throw new Exception("WHAT");
}

which would translate into:

if (!isValidXMLDocument)
{
throw new Exception("WHAT");
}


Collin

 

[Stefan Schulz]

It would be nice if you could extend the JLS with macros, or some sort
of pre-processor that would let you use:

Please not. Macros are rightfully viewed as a pest by most C programmers.
They are actually automatic source code rewriting, after all, often with
effects you never intended, like evaluating function calls several times.

 

[Darryl L. Pierce]

That should never happen, since the assignment doesn't return a boolean
value so the code won't compile.

 

[Antti S. Brax]

That should never happen, since the assignment doesn't return a boolean
value so the code won't compile.

Maybe you should have tried to compile it.

Hint: it does compile and work as advertised.

 

[Darryl L. Pierce]

Strange. I stand corrected.

 

[Antti S. Brax]

Strange. I stand corrected.

You were propably thinking about C-like if statements.

int i = 1;
if (i = 0) {
// Not valid Java code.
}

 

[Bent C Dalager]

You were propably thinking about C-like if statements.

int i = 1;
if (i = 0) {
// Not valid Java code.
}

Of course, the reason Java isn't vulnerable to this is that it doesn't
auto-cast int to bool like C does. It _does_, however, "auto-cast"
bool to bool (heh) and so it is vulnerable in the case of boolean
conditionals/assignments.

The following demonstrates that the assignment operator does evaluate
to a value just as in C:

public class Test
{
public static void main(String[] args)
{
int i = 3;
System.out.println("It is " + (i = 5));
}
}

which outputs
It is 5

Cheers
Bent D

 

[Tony Morris]

Of course, the reason Java isn't vulnerable to this is that it doesn't

auto-cast int to bool like C does.

WTF?
Since when did C have a bool (or smantically equivalent) type?

 

[Bent C Dalager]

WTF?
Since when did C have a bool (or smantically equivalent) type?

It acquired the concept the instant someone defined a language
construct that depends upon the truth-value of some expression. "if"
would be one such construct.

The primary mistake with C in this regard was to allow just about
anything under the sun to evaluate to a truth-value. The mistake with
Java was to let assignments have a value at all. In both cases, the
end result is to let programmers create hard-to-find bugs by confusing
assignment operators with comparison operators.

Cheers
Bent D

 

[Tor Iver Wilhelmsen]

The primary mistake with C in this regard was to allow just about
anything under the sun to evaluate to a truth-value.

Not as long as it's consistent. Like "nil vs. non-nil" values in Lisp.

The mistake with Java was to let assignments have a value at all. In
both cases, the end result is to let programmers create hard-to-find
bugs by confusing assignment operators with comparison operators.

Java inherited the C curse there, yes. Other languages differentiate
better by using := for assignment. As for letting assignment return,
it's convenient the few times you want to set lots of variables at
once to the same value...

E.g. for using a local (stack) ref of a value assigned to a field:

String foo = name = "Test";

 

[Grant Wagner]

Not as long as it's consistent. Like "nil vs. non-nil" values in Lisp.


Java inherited the C curse there, yes. Other languages differentiate
better by using := for assignment. As for letting assignment return,
it's convenient the few times you want to set lots of variables at
once to the same value...

E.g. for using a local (stack) ref of a value assigned to a field:

String foo = name = "Test";

Or when you want to write:

while ((line= br.readLine()) != null)

 

[=?ISO-8859-1?Q?S=E9bastien_Auvray?=]

ronron a écrit :

I tried to search the usenet for the same question...

Well I would like to know which is the coding style that you prefer

boolean booleanValue=getABooleanValue();
if (!booleanValue) {
doSomething();
}

Or

boolean booleanValue=getABooleanValue();
if (booleanValue == false) {
doSomething();
}

Pfffffffffffffffff... Who cares ???