"Condition is Always False" Question

[Brian]

I am using Borland C++ Builder 5 for my application. When I build my
application, it states that I have several if-statements that will
always be false. The statements appear correct, so could someone
please enlighten me as to how C++ Builder may think that the
conditions will always be false. See below. Thanks.

<snip>
td.expMon = trk2[9] * 10 + trk2[10];

// Borland says this is always false, though the condition is
fine.
if ((td.expMon < 0) || (td.expMon 12)) {
err = TKT_INVALID_MON TH;
}
</snip>

<snip>
td.expDay = trk2[11] * 10 + trk2[12];

// Borland says this is always false, though the condition is
fine.
if ((td.expDay < 0) || (td.expDay 31)) {
err = TKT_INVALID_DAY ;
}
</snip>

<snip>
td.eftvDay = trk2[28] * 10 + trk2[29];
// Borland says this is always false, though the condition is
fine.
if ((td.eftvDay < 0) || (td.eftvDay 31)) {
err = TKT_INVALID_DAY ;
}
</snip>

[Victor Bazarov]

Brian wrote:

I am using Borland C++ Builder 5 for my application. When I build my
application, it states that I have several if-statements that will
always be false. The statements appear correct, so could someone
please enlighten me as to how C++ Builder may think that the
conditions will always be false. See below. Thanks.

See below.

>
<snip>
td.expMon = trk2[9] * 10 + trk2[10];

// Borland says this is always false, though the condition is
fine.
if ((td.expMon < 0) || (td.expMon 12)) {

What's the type of 'expMon'? If it's unsigned, it cannot be less
that 0, so the first expression is always false.

err = TKT_INVALID_MON TH;
}
</snip>

<snip>
td.expDay = trk2[11] * 10 + trk2[12];

// Borland says this is always false, though the condition is
fine.
if ((td.expDay < 0) || (td.expDay 31)) {

Same here. How is 'expDay' declared? If it's unsigned, it cannot
be less than 0, so the first condition will always be false.

err = TKT_INVALID_DAY ;
}
</snip>

<snip>
td.eftvDay = trk2[28] * 10 + trk2[29];
// Borland says this is always false, though the condition is
fine.
if ((td.eftvDay < 0) || (td.eftvDay 31)) {

Same here.

err = TKT_INVALID_DAY ;
}
</snip>

HTH

V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask

[Andre Kostur]

"Brian" <bw******@gmail .comwrote in news:1171290076 .470125.49620
@q2g2000cwa.goo glegroups.com:

I am using Borland C++ Builder 5 for my application. When I build my
application, it states that I have several if-statements that will
always be false. The statements appear correct, so could someone
please enlighten me as to how C++ Builder may think that the
conditions will always be false. See below. Thanks.

<snip>
td.expMon = trk2[9] * 10 + trk2[10];

// Borland says this is always false, though the condition is
fine.
if ((td.expMon < 0) || (td.expMon 12)) {
err = TKT_INVALID_MON TH;
}
</snip>

<snip>
td.expDay = trk2[11] * 10 + trk2[12];

// Borland says this is always false, though the condition is
fine.
if ((td.expDay < 0) || (td.expDay 31)) {
err = TKT_INVALID_DAY ;
}
</snip>

<snip>
td.eftvDay = trk2[28] * 10 + trk2[29];
// Borland says this is always false, though the condition is
fine.
if ((td.eftvDay < 0) || (td.eftvDay 31)) {
err = TKT_INVALID_DAY ;
}
</snip>

We're not mind-readers.... you haven't told us what the types of expMon,
expDay, or eftwDay are. But my first guess would be that they are all
of some sort of unsigned type, thus all of your "< 0" comparisions will
always be false.

[Brian]

On Feb 12, 9:29 am, Andre Kostur <nntps...@kostu r.netwrote:

"Brian" <bwilk...@gmail .comwrote in news:1171290076 .470125.49620
@q2g2000cwa.goo glegroups.com:

I am using Borland C++ Builder 5 for my application. When I build my
application, it states that I have several if-statements that will
always be false. The statements appear correct, so could someone
please enlighten me as to how C++ Builder may think that the
conditions will always be false. See below. Thanks.

<snip>
td.expMon = trk2[9] * 10 + trk2[10];

// Borland says this is always false, though the condition is
fine.
if ((td.expMon < 0) || (td.expMon 12)) {
err = TKT_INVALID_MON TH;
}
</snip>

<snip>
td.expDay = trk2[11] * 10 + trk2[12];

// Borland says this is always false, though the condition is
fine.
if ((td.expDay < 0) || (td.expDay 31)) {
err = TKT_INVALID_DAY ;
}
</snip>

<snip>
td.eftvDay = trk2[28] * 10 + trk2[29];
// Borland says this is always false, though the condition is
fine.
if ((td.eftvDay < 0) || (td.eftvDay 31)) {
err = TKT_INVALID_DAY ;
}
</snip>

We're not mind-readers.... you haven't told us what the types of expMon,
expDay, or eftwDay are. But my first guess would be that they are all
of some sort of unsigned type, thus all of your "< 0" comparisions will
always be false.- Hide quoted text -

- Show quoted text -

Ok, yep that is what it was. They are all ushort. Makes total sense
now. I'll clarify better next time I ask a question.

[peter koch]

On Feb 12, 3:29 pm, Andre Kostur <nntps...@kostu r.netwrote:

"Brian" <bwilk...@gmail .comwrote in news:1171290076 .470125.49620
@q2g2000cwa.goo glegroups.com:

I am using Borland C++ Builder 5 for my application. When I build my
application, it states that I have several if-statements that will
always be false. The statements appear correct, so could someone
please enlighten me as to how C++ Builder may think that the
conditions will always be false. See below. Thanks.

<snip>
td.expMon = trk2[9] * 10 + trk2[10];

// Borland says this is always false, though the condition is
fine.
if ((td.expMon < 0) || (td.expMon 12)) {
err = TKT_INVALID_MON TH;
}

[snips]

>
We're not mind-readers.... you haven't told us what the types of expMon,
expDay, or eftwDay are. But my first guess would be that they are all
of some sort of unsigned type, thus all of your "< 0" comparisions will
always be false.

I might have a blind spot here, but this would still leave the other
part of the condition, e.g. (td.expMon 12) above.
Ahhh... perhaps the compiler complains about part of a boolean
expression? That would make sense (sort of).

/Peter

[Brian]

On Feb 12, 9:36 am, "peter koch" <peter.koch.lar [e-mail] ote:

On Feb 12, 3:29 pm, Andre Kostur <nntps...@kostu r.netwrote:

"Brian" <bwilk...@gmail .comwrote in news:1171290076 .470125.49620
@q2g2000cwa.goo glegroups.com:

I am using Borland C++ Builder 5 for my application. When I build my
application, it states that I have several if-statements that will
always be false. The statements appear correct, so could someone
please enlighten me as to how C++ Builder may think that the
conditions will always be false. See below. Thanks.

<snip>
td.expMon = trk2[9] * 10 + trk2[10];

// Borland says this is always false, though the condition is
fine.
if ((td.expMon < 0) || (td.expMon 12)) {
err = TKT_INVALID_MON TH;
}

[snips]

We're not mind-readers.... you haven't told us what the types of expMon,
expDay, or eftwDay are. But my first guess would be that they are all
of some sort of unsigned type, thus all of your "< 0" comparisions will
always be false.

I might have a blind spot here, but this would still leave the other
part of the condition, e.g. (td.expMon 12) above.
Ahhh... perhaps the compiler complains about part of a boolean
expression? That would make sense (sort of).

/Peter- Hide quoted text -

- Show quoted text -

Correct me if I'm wrong, but if I also try to assign a negative number
to this variable, the negative number will be assessed as the unsigned
value. So if I tried to assign -1, it should be assessed as the
unsigned value of 65,535.

[Victor Bazarov]

Brian wrote:

[..]
Correct me if I'm wrong, but if I also try to assign a negative number
to this variable, the negative number will be assessed as the unsigned
value. So if I tried to assign -1, it should be assessed as the
unsigned value of 65,535.

Seems right if your 'unsigned short' is 16 bits long.

V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask

[Rolf Magnus]

Victor Bazarov wrote:

Brian wrote:

>[..]
Correct me if I'm wrong, but if I also try to assign a negative number
to this variable, the negative number will be assessed as the unsigned
value. So if I tried to assign -1, it should be assessed as the
unsigned value of 65,535.

Seems right if your 'unsigned short' is 16 bits long.

.... and the signed one is stored in 2's complement.

[Victor Bazarov]

Rolf Magnus wrote:

Victor Bazarov wrote:

>Brian wrote:

>>[..]
Correct me if I'm wrong, but if I also try to assign a negative
number to this variable, the negative number will be assessed as
the unsigned value. So if I tried to assign -1, it should be
assessed as the unsigned value of 65,535.

Seems right if your 'unsigned short' is 16 bits long.

... and the signed one is stored in 2's complement.

Actually, that doesn't matter. The standard guarantees the 'modulo
2^n' operation regardless of the representation. The bit pattern
doesn't change for 2's complement (it does for the other two reps).

V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask

[Clark S. Cox III]

Rolf Magnus wrote:

Victor Bazarov wrote:

>Brian wrote:

>>[..]
Correct me if I'm wrong, but if I also try to assign a negative number
to this variable, the negative number will be assessed as the unsigned
value. So if I tried to assign -1, it should be assessed as the
unsigned value of 65,535.

Seems right if your 'unsigned short' is 16 bits long.

.... and the signed one is stored in 2's complement.

That is irrelevant. On *any* C implementation (regardless of the
representation of signed integers), the value (-1), when converted to an
unsigned type will be converted to the maximum value representable by
that type. Period.
--
Clark S. Cox III
cl*******@gmail .com