AVR-Chat

Thanks guys!  I was thinking in the c++ world again...




--- In AVR-Chat@yahoogroups.com, Martin McKee  wrote:
>
> Pass-by-reference is only available in C++.  In C you have to pass in a
> pointer, and, for that, you use * as has been mentioned.
> 
>  void CalculateOffTime( uint8_t duration, offTimeStruct* eventOff )
> 
> then, eventOff->endMinute = ...
> 
> Martin Jay McKee
> 
> On Sat, Feb 2, 2013 at 2:22 PM, Charlie H  wrote:
> 
> > **
> >
> >
> > I agree with Clark on the pointer issue. The & should be * in the
> > function declaration.
> >
> > Charlie
> >
> >
> > On 2/2/2013 4:17 PM, englsprogeny1 wrote:
> > >
> > > I've updated the struct, thanks.
> > >
> > > I want to be able to update the values within the struct (depending on
> > what 'instance' is passed into the function).
> > >
> > > This is why I am doing 'pass by reference' (by the address)
> > >
> > >
> > > I get the following error:
> > >
> > > menu.c:1732: error: expected ';', ',' or ')' before '&' token
> > >
> > > This is referring to the prototype portion of the function definition.
> > >
> > >
> > >
> > > void CalculateOffTime(uint8_t duration, offTimeStruct &eventOff)
> > >
> > >
> > >
> > > Any more ideas?
> > >
> > >
> > >
> > > --- In AVR-Chat@yahoogroups.com, Charlie H wrote:
> > >> It looks like you are expecting the address of the struct passed to your
> > >> function but not using the address in the function. Try it this way:
> > >>
> > >> void CalculateOffTime(uint8_t duration, offTimeStruct eventOff)
> > >> {
> > >> ...
> > >> }
> > >>
> > >>
> > >> Also, I think the typedef is wrong. Try it this way:
> > >>
> > >> typedef struct
> > >> {
> > >> uint8_t endMinute;
> > >> uint8_t endHour;
> > >> } offTimeStruct;
> > >>
> > >>
> > >> HTH,
> > >> Charlie
> > >>
> > >>
> > >> On 2/2/2013 2:51 PM, englsprogeny1 wrote:
> > >>> Simple C question.. I guess that I am blowing! Maybe I didn't get
> > enough sleep last night....
> > >>>
> > >>>
> > >>> Using AVR Studio 4.0 with GCC
> > >>>
> > >>> 1. I create a type that is a struct
> > >>> 2. I create multiple 'instances' of this type.
> > >>>
> > >>>
> > >>> I get the following errors when I Build All:
> > >>>
> > >>> menu.c:1729: error: expected declaration specifiers or '...' before
> > 'offTimeStruct'
> > >>> menu.c:1742: error: 'eventOff' undeclared (first use in this function)
> > >>>
> > >>>
> > >>>
> > >>>
> > >>> typedef struct offTimeStruct
> > >>> {
> > >>> uint8_t endMinute;
> > >>> uint8_t endHour;
> > >>> };
> > >>>
> > >>> offTimeStruct light1;
> > >>> offTimeStruct rocket;
> > >>>
> > >>>
> > >>>
> > >>> //menu.c: Line 1729
> > >>> void CalculateOffTime(uint8_t duration, offTimeStruct &eventOff)
> > >>> {
> > >>> //menu.c: Line 1742
> > >>> eventOff.endMinute = 1;
> > >>>
> > >>> }
> > >>>
> > >>>
> > >>>
> > >>>
> > >>> funtion call from Main()
> > >>>
> > >>>
> > >>> CalculateOffTime(1, light1);
> > >>>
> > >>> Thanks for your ideas guys!
> > >>>
> > >>>
> > >>>
> > >>>
> > >>>
> > >>> ------------------------------------
> > >>>
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> > >>>
> > >>>
> > >>>
> > >>>
> > >
> > >
> > >
> > > ------------------------------------
> > >
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> > >
> > >
> > >
> >
> >  
> >
> 
> 
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>