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Arclite
Joined: 02 Jul 2004
Posts: 16
Location: UK
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| Basic problem with Structures |
 Posted: Mon Jul 19, 2004 2:33 pm |
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Hi guys,
I havn't used PCWH for long and i need to know how to pass a structure
as a parameter of a function. I'm told by the compiler that i can't pass structs as parameters, so what is the method? I have no problems with pointers if required
I have:
struct Point
{
int16 X;
int16 Y;
int16 Z;
} NewPnt, LastPnt;
//---------------
Interpolate(struct Point A, struct Point B)
{
int16 Gradient;
// do stuff with A.X, ,A.Y, A.Z, and B.X, B.Y, B.Z
Gradient = A.X -B.X;
blah, blah, blah...
}
//---------------
void Main()
{
Interpolate(NewPnt,LastPnt);
} |
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Ttelmah
Guest
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| Re: Basic problem with Structures |
| Posted: Mon Jul 19, 2004 3:01 pm |
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| Arclite wrote: | Hi guys,
I havn't used PCWH for long and i need to know how to pass a structure
as a parameter of a function. I'm told by the compiler that i can't pass structs as parameters, so what is the method? I have no problems with pointers if required
I have:
struct Point
{
int16 X;
int16 Y;
int16 Z;
} NewPnt, LastPnt;
//---------------
Interpolate(struct Point A, struct Point B)
{
int16 Gradient;
// do stuff with A.X, ,A.Y, A.Z, and B.X, B.Y, B.Z
Gradient = A.X -B.X;
blah, blah, blah...
}
//---------------
void Main()
{
Interpolate(NewPnt,LastPnt);
} |
As you say, use pointers.
Code the definition as:
Interpolate(struct Point *A, struct Point *B)
code the call as:
Interpolate(&NewPnt,&LastPnt);
Inside the routine, code the actions on the structure, using the '->' construct, instead of the '.'. So:
Gradient = A->X -B->X;
If you want to return a structure, code the defintion as:
struct Point * Interpolate(struct Point *A, struct Point *B)
Inside the routine, declare a _static_ structure to contain the result, and put the values into this, say:
static struct Point result;
Then write to the elements of this as needed, and at the end of the routine, return the address of this with:
return(&result);
In the main routine, have a variable to hold this address, defined as:
struct Point * result_val;
And again talk to the elements with:
result_val->X etc.
Best Wishes |
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kypec
Joined: 20 Sep 2003
Posts: 54
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| another apporach |
| Posted: Tue Jul 20, 2004 1:53 am |
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I have coded it in my program like this:
| Code: |
void interpolate(struct point &a,struct point &b) {
int16 gradient;
gradient=a.x-b.x;
}
//function is called later like this
interpolate(a,b);
|
for me it is more convenient and readable, try it if you like  |
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Arclite
Joined: 02 Jul 2004
Posts: 16
Location: UK
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| Tried and trusted |
| Posted: Tue Jul 20, 2004 4:15 am |
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Thanks for the responses,
Ttelmah:
I've tried your approach, and it works. No surprise given that i had not read the manual on '->'. I've made much headway on a single chip 3 axis controller for that.
And again, thanks.
kypec:
I understand your method, the only problem being that i need to isolate the RAM within the function when i use/modify it. I therefore use scratch memory (i think that is what it's called) to for local variables help troubleshoot the code. Secondly, the code will be used for a larger number of axes in the future (6-10), so it helps now to make thing water tight.
Thanks to you too. |
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