Differences between gsl::span and proposed ranges?

[Christopher Horvath]

Hey Folks,

I feel like the concepts implemented in the "span" classes in the Core Guidelines and the gsl library are a small subset of the functionality that will be introduced when the ranges/v3 proposal is finally added to the language.

Am I incorrect in thinking this? 

Chris

[Nicol Bolas]

`span` is a concrete class (well, it's a template class but you know what I mean) which has specific functionality. "Ranges" are concepts; they represent patterns that other datatypes can implement.

A `span` is a range type, but not all ranges are `span`s. `vector`, `list`, and the other containers are also ranges.

The Ranges TS does not provide `span` or anything like `span` as a type. Indeed, if I recall correctly, the current Ranges TS doesn't provide any range types at all. Such types are reserved for the next version of the proposal.

I don't believe that Boost.Range provides anything quite like `span` either. While it does have iterator ranges, it doesn't have a range type that restricts itself to contiguous arrays only. `span` does.

So really, `span` has little to do with the Range TS, and it is not derived from it.

[Christopher Horvath]

Thank you!

I really like the span stuff as implemented in the GSL - however, I'm worried that adoption and support of GSL seems very polarized.

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