What I am doing wrong
This works
batPointer = adaptors[position].adaptor[channel]->batData;
adaptors[position].batteries[channel] = batPointer->battery;
where:
batData is a pointer to a struct
batPointer is a pointer to a different kind of struct
I want one line, but I get compiler errors, what is the correct syntax?
7  2635 
Neil wrote:
What I am doing wrong
This works
batPointer = adaptors[position].adaptor[channel]->batData;
adaptors[position].batteries[channel] = batPointer->battery;
where:
batData is a pointer to a struct
batPointer is a pointer to a different kind of struct
I want one line, but I get compiler errors, what is the correct
syntax?
Please post a complete, minimal program that exhibits the concerned
error. Without precise definitions
of 'batPointer', 'adaptors', 'position', 'channel', 'batData',
and 'battery', we cannot say what the problem could be.
Neil wrote:
What I am doing wrong
This works
batPointer = adaptors[position].adaptor[channel]->batData;
adaptors[position].batteries[channel] = batPointer->battery;
where:
batData is a pointer to a struct
batPointer is a pointer to a different kind of struct
I want one line, but I get compiler errors, what is the correct syntax?
What was your one line, what were the declarations of the variables, and
what were the compiler errors?
[I'd also be likely to introduce a name for `adaptors[position]`, since it's
duplicated. And without seeing the rest of your code, I can't tell if your
assignment above should obviously be extracted into a well-named function
of its own.]
--
Chris "in some contexts, context is everything" Dollin
Hewlett-Packard Limited registered office: Cain Road, Bracknell,
registered no: 690597 England Berks RG12 1HN
Neil wrote:
....
The structs ( minus the uneeded stuff)are
struct adaptorBatteryD ata
{
struct batteryData const *battery;
};
struct adaptorData
{
struct adaptorBatteryD ata const *batData;
};
struct batteryData
{
};
struct adaptorBatteryD ata const *batPointer;
adaptors[position].batteries[channel] =
adaptors[position].adaptor[channel].batData->battery;
Gives the error "structure required on left side of . or *."
What is missing from what you just gave us is the data type for
adaptors[position] and adaptors[position].adaptor[channel]. As written,
your code requires that they both be structures. The message that was
generated implies that at least one of those expressions is a pointer to
a structure. If that is the case, then the your problem is due to the
fact that you've used "." rather than "->".
Neil <Ne*******@worl dnet.att.netwri tes:
Tomás Ó hÉilidhe wrote:
>Neil:
>> batPointer = adaptors[position].adaptor[channel]->batData;
adaptors[position].batteries[channel] = batPointer->battery;
I want one line, but I get compiler errors, what is the correct syntax?
[...]
>>
adaptors[position].batteries[channel] = adaptors[position].adaptor
[channel]->batData->battery;
I thought that, but then though it wrong. Thanks for the answer. And
the tip.
I hated to leave the two line solution.
Why? Is there some virtue in putting as much stuff as possible on one
line?
--
Keith Thompson (The_Other_Keit h) <ks***@mib.or g>
Looking for software development work in the San Diego area.
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"
On Thu, 29 Nov 2007 03:42:51 -0500, Neil <Ne*******@worl dnet.att.net>
wrote:
>What I am doing wrong
What is your end objective? What are really trying to accomplish?
>
This works
How can it work if you get compiler errors?
>
batPointer = adaptors[position].adaptor[channel]->batData;
adaptors[position].batteries[channel] = batPointer->battery;
where:
batData is a pointer to a struct
batPointer is a pointer to a different kind of struct
If batPointer is of type struct x* and batData is of type struct y*,
they are incompatible and there is no implicit conversion between
them. The only way to assign a value of one type to an object of
incompatible type is with a cast. However, if the converted pointer
value does not have the proper alignment you have invoked undefined
behavior.
Why do you want a pointer to some object to hold the address of an
object of different type?
>
I want one line, but I get compiler errors, what is the correct syntax?
One line of what? You have two independent assignment statements. Do
you intend to eliminate one?
Remove del for email
On Fri, 30 Nov 2007 02:53:53 -0500, Neil <Ne*******@worl dnet.att.net>
wrote:
snip
>Yes it works. The structures are elaborate ( Not mine ) but they do
want the are supposed to. Same the adapter, and the battery from the
linked list.
The structs ( minus the uneeded stuff)are
Unfortunately, also minus some needed stuff.
>
struct adaptorBatteryD ata
{
struct batteryData const *battery;
};
struct adaptorData
{
struct adaptorBatteryD ata const *batData;
};
struct batteryData
{
};
struct adaptorBatteryD ata const *batPointer;
adaptors[position].batteries[channel] =
You have not told us what type of struct the object adaptors is a
pointer to or an array of. The underlying structure apparently has a
member named batteries which does not match any of the three
structures you listed.
>adaptors[position].adaptor[channel].batData->battery;
It apparently also has a member named adaptor which also doesn't match
any of the three structures you listed. But adaptor appears to be an
array of or a pointer to struct adaptorData since it has a member
named batData.
batData is a pointer to struct adaptorBatteryD ata which does have a
member named battery. This member is a pointer to struct
batteryData.
So the first question: Is the undefined member batteries an object of
a suitable type so batteries[i] can receive a value of type pointer to
struct batteryData?
>Gives the error "structure required on left side of . or *."
C doesn't have an operator "*.". It does have two operators "*" but
neither one is applied to structures.
So the second question: What is the correct text of the error message?
Use cut and paste; don't retype.
And the third question: Which of the objects adaptors[i]. or
adaptor[i] is not a structure?
Remove del for email
Barry Schwarz wrote:
On Thu, 29 Nov 2007 03:42:51 -0500, Neil <Ne*******@worl dnet.att.net>
wrote:
>What I am doing wrong
What is your end objective? What are really trying to accomplish?
The pointer was use to search a linked list, If it fails I need the
first item as a place holder.
>This works
How can it work if you get compiler errors?
The two lines worked fine, When I tried to combine them I got the errors.
>
> batPointer = adaptors[position].adaptor[channel]->batData;
adaptors[position].batteries[channel] = batPointer->battery;
where:
batData is a pointer to a struct
batPointer is a pointer to a different kind of struct
If batPointer is of type struct x* and batData is of type struct y*,
they are incompatible and there is no implicit conversion between
them. The only way to assign a value of one type to an object of
incompatible type is with a cast. However, if the converted pointer
value does not have the proper alignment you have invoked undefined
behavior.
struct x* contains a pointer to a linked list of struct y* (struct x* is
also a linked list)
->a->b->c->d->NULL
| | | |
1 1 1 1
| | |
2 2 2
| |
3 3
>
Why do you want a pointer to some object to hold the address of an
object of different type?
>I want one line, but I get compiler errors, what is the correct syntax?
One line of what? You have two independent assignment statements. Do
you intend to eliminate one?
No combine
>
Remove del for email
The earlier suggestion worked fine. Thanks to all.
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