C18 compiler. struct issues. - Electronic Circuits Projects Diagrams Free

HerbertMunch · 30th December 2007, 04:17 AM

Im trying to make a member of this struct reference another instance of the same struct.

Code:

typedef struct MenuItem
{
	
	//Pointer to the an array of menuitems that represents the next level of heirarchy.
	MenuItem *nextLevel;
	
	

}MenuItem;

The compiler is not happy.
Can this not be done in c?

HerbertMunch · 30th December 2007, 04:28 AM

Would it be okay to do this instead, and then cast later?

Code:

typedef struct MenuItem
{
	
	//Pointer to the an array of menuitems that represents the next level of heirarchy.
	void *nextLevel;
	
	

}MenuItem;

Thanks

Pommie · 30th December 2007, 05:01 AM

Would it be,

Code:

typedef struct MenuItem
{
	
	//Pointer to the an array of menuitems that represents the next level of heirarchy.
	near rom * MenuItem;

}MenuItem;

Mike.

Pommie · 30th December 2007, 05:07 AM

BTW, I added a message print routine to your code that uses a rom pointer.

Code:

void PutMessage(char rom*);
void PutMessageAt(unsigned char,unsigned char,char rom*);


void main(void){
    InitLCD();
    PutMessage((rom char*) "Hello World!");
    PutMessageAt(3,2,(rom char*) "3 in on Line 2");
    while(1);
}

//Write a string to the LCD
void PutMessage(char rom *Message){
	while(*Message!=0)
	    WriteChar(*Message++);
}

//Set position and write string.
void PutMessageAt(unsigned char X,unsigned char Y,char rom *Message){
    WriteCommand(0x80+(--Y<<6)+--X);
	while(*Message!=0)
	    WriteChar(*Message++);
}

Mike.

HerbertMunch · 30th December 2007, 02:13 PM

Ok thanks mike.

out of interest, which memory would my old code point to?

Thanks.

Mike, K8LH · 30th December 2007, 02:28 PM

Quote:

Originally Posted by Pommie

BTW, I added a message print routine to your code that uses a rom pointer.

Code:

void PutMessage(char rom*);
void PutMessageAt(unsigned char,unsigned char,char rom*);


void main(void){
    InitLCD();
    PutMessage((rom char*) "Hello World!");
    PutMessageAt(3,2,(rom char*) "3 in on Line 2");
    while(1);
}

//Write a string to the LCD
void PutMessage(char rom *Message){
    while(*Message!=0)
        WriteChar(*Message++);
}

//Set position and write string.
void PutMessageAt(unsigned char X,unsigned char Y,char rom *Message){
    WriteCommand(0x80+(--Y<<6)+--X);
    while(*Message!=0)
        WriteChar(*Message++);
}

Mike.

Nicely done Mike. A wonderful example using pointers which has thus far eluded and confounded me.

Pommie · 30th December 2007, 03:27 PM

Pointers on the pic are confusing. The default is that pointers point to ram. I'm slowly getting comfortable with the types of pic pointers and have just realised that the cast on the function call is now not needed, this is from when I was trying everything to get it working.

So,

Code:

        PutMessage("Hello World!");

Should work fine.

Mike.

HerbertMunch · 31st December 2007, 02:44 AM

Quote:

Originally Posted by Pommie

Pointers on the pic are confusing. The default is that pointers point to ram. I'm slowly getting comfortable with the types of pic pointers and have just realised that the cast on the function call is now not needed, this is from when I was trying everything to get it working.

So,

Code:

        PutMessage("Hello World!");

Should work fine.

Mike.

ok thanks very much mate.

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30th December 2007, 04:17 AM	(permalink)
HerbertMunch	C18 compiler. struct issues. Im trying to make a member of this struct reference another instance of the same struct. Code: typedef struct MenuItem { //Pointer to the an array of menuitems that represents the next level of heirarchy. MenuItem *nextLevel; }MenuItem; The compiler is not happy. Can this not be done in c?

30th December 2007, 04:28 AM	(permalink)
HerbertMunch	Would it be okay to do this instead, and then cast later? Code: typedef struct MenuItem { //Pointer to the an array of menuitems that represents the next level of heirarchy. void *nextLevel; }MenuItem; Thanks

30th December 2007, 05:01 AM	(permalink)
Pommie	Would it be, Code: typedef struct MenuItem { //Pointer to the an array of menuitems that represents the next level of heirarchy. near rom * MenuItem; }MenuItem; Mike.

30th December 2007, 02:13 PM	(permalink)
HerbertMunch	Ok thanks mike. out of interest, which memory would my old code point to? Thanks.

30th December 2007, 03:27 PM	(permalink)
Pommie	Pointers on the pic are confusing. The default is that pointers point to ram. I'm slowly getting comfortable with the types of pic pointers and have just realised that the cast on the function call is now not needed, this is from when I was trying everything to get it working. So, Code: PutMessage("Hello World!"); Should work fine. Mike.