what is the i result and why?

int k = 1;
int i = ++k + k++ + (+)k;

when i run the code in visual age for java 3.0, the result is 5.
when i run the code using jdk1.2 complier. i got result 7.
that means same code run under different virture machine will result different result.
is that a virture machine bug?
can anyone tell me?

The first rule of thumb is (I am sure you all are aware of) -

"Operands are evaluated first from left to right, and then
associativity is performed from right to left."

The second rule of thumb is -

"Compilers have differences in interpreting
complicated/abusive codes (no offense)".

Before I get to Peter's question, lets try this simple example.

int[] a = {2,2};
int i = 1;

a[i] = i = 0;

As a result of the third statement, the array will be now {2,0},
and not {0,2}.

Applying the same rule to Peter's code:
int k = 1;
int i = ++k + k++ + +k;

we get
i = (++k) + k + (++(+k))
or, i = 2 + 2 + 3
or, i = 7

The confusion is about how the compiler interpretes the
operators between the second k and the third k. We'd think
the second k should get a post-fix incrementer and the
third k should get only a unary plus. This would have been
true if the two operands are different.

x++ + +y is interpreted as (x++) + (+y)

but,

x++ + +x is interpreted as (x) + (++(+x)).

Also, we have to remember that when you have even number
of operators between two operands, the second operand gets
a unary operator, and it needs a whitespace before it.
(x++++x) will not compile, but (x+++ +x) and (x+++x) will. Again, some compilers may choose to differ.

Anyways, these codes stretch the compiler to the limit,
and I hope we won't see any code like these in the real
business world.

But, I've to say, Peter, its a good one. If you are upto
the challenge, try this ....

a = b ? c : d ? e : f ? g : h ? i : j;

Thank you, all.

quote:

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Originally posted by peter_gong01:
int k = 1;
int i = ++k + k++ + +k;

what is the i result and why?

[This message has been edited by peter_gong01 (edited May 13, 2000).]

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Regds.

Can you be little bit elaborate on what you are trying to say?

quote:

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int k = 1;
k = ++k + k++ + k ;
System.out.println(k);
when i run the code in visual age for java 3.0, the result is 5.
when i run the code using jdk1.2 complier. i got result 7.

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When I executed the the above expression in VA for Java 3.0, I got the answer as 7. though I was clear on why it was 7, the above remark by U thet U are getting different results prompted me to test in VA for Java.
But for the purpose of the Certification we should assume that we have just JDK 1.2 and nothing else I THINK.