Guys,

quick question - got a function like:

void CalculateApproach(float (&Params)[4], double (&ObjectPos)[3],
double (&VehiclePos)[4], double (&NewPos)[4])


OK, the seconds argument should come from an array but this array is
bigger than the expected 3 i.e it has 10 elements but I only need 4,5
and 6 so I tried something like:

CalculateApproach(fAppParams, &dFeatures[4], dCurVehPos, dNewVehPos);

but it fails for me. Am I trying to do something that is not allowed and
hence should just make new array[3] and copy my values in and then pass
it into the function or can someone give me hint towards the syntax i
should be using if it can work?



Cheers,


John.

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In article <XVqni.57$SI5.43@newsfe2-gui.ntli.net>, john
<reply@newsgroup.com> wrote:

> Guys,
>
> quick question - got a function like:
>
> void CalculateApproach(float (&Params)[4], double (&ObjectPos)[3],
> double (&VehiclePos)[4], double (&NewPos)[4])
>
>
> OK, the seconds argument should come from an array but this array is
> bigger than the expected 3 i.e it has 10 elements but I only need 4,5
> and 6 so I tried something like:
>
> CalculateApproach(fAppParams, &dFeatures[4], dCurVehPos, dNewVehPos);
>
> but it fails for me. Am I trying to do something that is not allowed and
> hence should just make new array[3] and copy my values in and then pass
> it into the function or can someone give me hint towards the syntax i
> should be using if it can work?
>
  typedef double DoubleFour[4];
  typedef double DoubleThree[3];

   void  CalculateApproach(DoubleFour &,DoubleThree &,DoubleFour
&,DoubleFor &);

    CalculateApproach(fAppParams, (DoubleThree &)(dFeatures[4]),
dCurVehPOs,dNewVehPos);

 this should work, as an array must be decayable to a pointer so the
cast is only to tell the compiler what is going on.  A reinterpret_cast
will be needed and this is a strong warning that it might not be
portable.

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"john" <reply@newsgroup.com> wrote in message
news:XVqni.57$SI5.43@newsfe2-gui.ntli.net...
> Guys,
>
> quick question - got a function like:
>
> void CalculateApproach(float (&Params)[4], double (&ObjectPos)[3], double
> (&VehiclePos)[4], double (&NewPos)[4])
>
>
> OK, the seconds argument should come from an array but this array is
> bigger than the expected 3 i.e it has 10 elements but I only need 4,5 and
> 6 so I tried something like:
>
> CalculateApproach(fAppParams, &dFeatures[4], dCurVehPos, dNewVehPos);

Calculateapproache( float&* fAppParams, double& dFeatures[4], double&*
dcurVehPos, double&* dNewVehPos )

> but it fails for me. Am I trying to do something that is not allowed and
> hence should just make new array[3] and copy my values in and then pass it
> into the function or can someone give me hint towards the syntax i should
> be using if it can work?
>
>
>
> Cheers,
>
>
> John.
>
> ---
> [ comp.std.c++ is moderated.  To submit articles, try just posting with ]
> [ your news-reader.  If that fails, use mailto:std-c++@ncar.ucar.edu    ]
> [              --- Please see the FAQ before posting. ---               ]
> [ FAQ: http://www.comeaucomputing.com/csc/faq.html                      ]
>

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john wrote:
> Guys,
>
> quick question - got a function like:
>
> void CalculateApproach(float (&Params)[4], double (&ObjectPos)[3],
> double (&VehiclePos)[4], double (&NewPos)[4])
>
>
> OK, the seconds argument should come from an array but this array is
> bigger than the expected 3 i.e it has 10 elements but I only need 4,5
> and 6 so I tried something like:
>
> CalculateApproach(fAppParams, &dFeatures[4], dCurVehPos, dNewVehPos);
>
> but it fails for me. Am I trying to do something that is not allowed and
> hence should just make new array[3] and copy my values in and then pass
> it into the function or can someone give me hint towards the syntax i
> should be using if it can work?
>
>
>
> Cheers,
>
>
> John.


Thanks guys, the cast worked.  I thought I could use a cast but was
unsure about the syntax but using the typedef sorted it!

Thanks again.


John.

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On Jul 18, 6:52 pm, re...@newsgroup.com (john) wrote:

> void CalculateApproach(float (&Params)[4], double (&ObjectPos)[3],
> double (&VehiclePos)[4], double (&NewPos)[4])
>
> OK, the seconds argument should come from an array but this array is
> bigger than the expected 3 i.e it has 10 elements but I only need 4,5
> and 6 so I tried something like:
>
> CalculateApproach(fAppParams, &dFeatures[4], dCurVehPos, dNewVehPos);
>
> but it fails for me. Am I trying to do something that is not allowed

Yes.
The type of &dFeatures[4] is double*, with certainly isn't an array of
three doubles or a reference to one, but only a pointer to a double.

> and
> hence should just make new array[3] and copy my values in and then pass
> it into the function

That's a possible solution.


> or can someone give me hint towards the syntax i
> should be using if it can work?

You could use some reinterpret_casts, but that's evil too.
The correct way would probably be to design your function differently.

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