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Re: [MANTA] unnamed in PointVector


Chronological Thread 
  • From: Christiaan Paul Gribble <cgribble@sci.utah.edu>
  • To: James Bigler <bigler@cs.utah.edu>
  • Cc: "'manta@sci.utah.edu'" <manta@sci.utah.edu>
  • Subject: Re: [MANTA] unnamed in PointVector
  • Date: Tue, 24 May 2005 15:15:48 -0600
Looks like a compile-time check on the dimensionality of the vector to
me.  Anyway, it reminds me of Andrew's trick for the scratchpad size
that floated on the cs6620 list last spring:

  template<typename T>
  const T* HitRecord::getScratchpad(void) const {
    // Compile time check
    typedef char unused[(sizeof(T)<=MAX_SCRATCHPAD_SIZE)?1:0];

    return reinterpret_cast<const T*>(scratch);
  }

In this case, if Dim == 3, char unnamed[1] will be a valid (but ignored)
variable, and if Dim != 3, char unnamed[0] will throw up a red flag...

C

James Bigler wrote:
> What is the purpose of unnamed in PointVector.h?  It doesn't seem to be
> referenced.  Here's an example from line 22:
> 
>     VectorT(T x, T y, T z) {
>       char unnamed[ Dim == 3 ? 1 : 0 ];
>       data[0] = x; data[1] = y; data[2] = z;
>     }
> 
> Thanks,
> James



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