What is a Closure Type? Understanding Boost uBLAS

[Hurkyl]

What is a "closure type"?

I first encountered it by looking at the source of the uBLAS package from boost.org -- it's essentially an implementation of the BLAS using expression templates.

I noticed that a lot of the classes have a nested typedef called "closure_type" (and a "const_closure_type"), and I've never heard of such a thing.

Also, a couple of the classes define a "same_closure" member function which simply tests for identity. For example, from the "scalar_value" class:

        bool same_closure (const scalar_value &sv) const {
            return this == &sv;    // self closing on instances value
        }

And I haven't yet managed to discover the purpose of such a thing by looking through the source code, nor by googling for "closure type". (I get hits on closure type, but not enough info to infer what such a thing is, and the point of it)

Does anyone here know?

 

[pallidin]

Because it's a non-standard coding to establish parameters to terminate an argument.

 

[Hurkyl]

Could you say that again?