Re: [Blitz-support] Testing Conditionals With TinyVector

[Patrik J. <co...@fa...>]

Hi John,

Won't just blitz::all and blitz::any (as in "blitz::all(v == w)") work?

Also, the appearance of _bz_VecExpr seems to indicate that you are
using the very old blitz 0.9. I'd encourage you to upgrade.

cheers,

/Patrik

On Tue, Jul 10, 2012 at 5:26 PM, John Dickson <joh...@gm...> wrote:
> It seems natural to use blitz::product and blitz::sum as "and" and "or",
> respectively, on TinyVectors of type bool. (That is, blitz::product(v)
> returns 1 if all entries in v are true and 0 otherwise, and similarly with
> and.) This is particularly useful when comparing two vectors in an if
> statement, as in
>
> if (blitz::product(v == w)) { ... }
>
> However, with g++ -- and at least some versions of MSVC -- the above
> expression (where v and w are TinyVector<int,3>) results in the compiler
> error message:
>
> "... error: no matching function for call to
> product(blitz::_bz_VecExpr<blitz::_bz_VecExrOp<blitz::TinyVector<IterConst<int,
> 3, 1>, blitz::TinyVectorIterConst<int, 3, 1>, blitz::_bz_Equal<int,int> > >"
>
> The above is readily fixed by enclosing v == w in a static_cast, as in:
>
> if (blitz::product(static_cast<blitz::TinyVector<bool,3> >(v == w))) { ... }
>
> but this is clumsy when comparisons are made frequently. Note that similar
> problems occur with any function that accepts a TinyVector as an argument
> when passed a TinyVector expression.
>
> Thus my question is: is there any way to avoid the static_cast when passing
> an expression to either the blitz built-in functions like product and sum or
> to other functions that accept a TinyVector as an argument?
>
> Thank you,
> John
>
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