Building, say, indices<6,4,2,0,-2,-4>

I have moved my blog to Github. You can find this post at https://pkeir.github.io/blog/2012/12/03/building-indices.

2 thoughts on “Building, say, indices<6,4,2,0,-2,-4>”

R. Martinho Fernandes says:

December 3, 2012 at 12:07 pm

> the select function can be typed just as effectively by the more ornate code below.

This is not true. That code is not correct in the general case. As a start, that implementation of select is not the best, but ignoring that for a moment, the second version does not always behave like the first one.

The assertions in this program hold: http://stacked-crooked.com/view?id=2383053c85152e4695364e32ce1688df. That actually means the second version does not compile in the presence of tuples references: http://stacked-crooked.com/view?id=8b4471beb5cd06a55853a04e9a483f4c. And there are other behaviours of the first version that the second version does not emulate, namely those concerning std::reference_wrapper.

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1. pgkpgk says:
  
  December 3, 2012 at 11:19 pm
  
  Thankyou, you are correct. I’m not so interested in reference arguments here, so I’ve simply updated the return type of the non-decltype version to also decay (using std::decay) the tuple elements. I’m actually quite pleased that it’s now more verbose, as it emphasises my preference here for the use of decltype. I’ve given stacked-crooked.com a whirl with my own test here.
  
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