Generic functor holder and constant image from functor.

[rolanddenis]

PR Description

This PR adds:

• FunctorHolder: hold any callable object (function, functor, lambda, ...) as a C(Unary)Functor model without relying on std::function
• FunctorConstImage: Transform a point-dependant functor into a constant image.
• PointFunctorHolder: hold any callable object, that accept a point, as a CPointFunctor model
• a module page about functions, functors and lambdas in DGtal.

Checklist

• Unit-test of your feature with Catch.
• Doxygen documentation of the code completed (classes, methods, types, members...)
• Documentation module page added or updated.
• New entry in the ChangeLog.md added.
• No warning raised in Debug cmake mode (otherwise, Travis C.I. will fail).
• All continuous integration tests pass (Travis & appveyor)
• Example file
• Module page about passing function as parameter

[dcoeurjo]

Thx Roland for the PR !

[rolanddenis]

I'm writing a huge documentation about FunctorHolder, its usage and how to make a custom CUnaryFunctor model that rely on it ... maybe it would be better to put that doc in a dedicated page, like "Using functions, functors and lambdas in DGtal with FunctorHolder" ?

[dcoeurjo]

Definitely agree... please do so

[dcoeurjo]

BTW I don't think we have any doc on all functions in BasicPointFunctors, BasicPointPredicates... beside the functors namespace

[rolanddenis]

So we should choose a more generic name, like "Using functions, functors and lambdas in DGtal", starting with a list of available functors and ending with the current documentation of FunctorHolder about how creating its own DGtal compatible functors ?

[dcoeurjo]

Yep

[dcoeurjo]

thx

[rolanddenis]

Documentation moved (without the functors list)

[JacquesOlivierLachaud]

Seems perfect to me. The doc module is very complete and very clear. Congrats !
I wait for David's comments before merging.

[dcoeurjo]

(my comments on the Changleog were due to a pending review.. I'll continue my review)

[dcoeurjo]

Comments on the doc (I've tried the new github suggestion for the typos..)

[rolanddenis]

Before merging, this PR may need to change its naming convention:

• the CUnaryFunctor model is FunctorHolder (but it is not only for unary functors) with construction helper called holdFunctor,
• the CPointFunctor model is PointFunctorHolder with construction helper called makePointFunctorHolder,
• the CConstImage model is FunctorConstImage with construction helper called makeFunctorConstImage.

What do you think ?

[JacquesOlivierLachaud]

This PR looks ready to be merged for me. @dcoeurjo Are you ok ?

[dcoeurjo]

Fine for me but @rolanddenis has pending questions I think

[dcoeurjo]

@rolanddenis can you please update this branch w.R.t. the master ?

[rolanddenis]

Done

[rolanddenis]

About my previous question, I was thinking about a naming like that:

• FunctorHolder and holdFunctor
• maybe an alias to be consistent: UnaryFunctorHolder and holdUnaryFunctor
• PointFunctorHolder and holdPointFunctor
• ConstImageFunctor (and/or Holder ?) (instead of FunctorConstImage) and holdConstImageFunctor

[rolanddenis]

I have modified the naming scheme accordingly to my last comment (except for the UnaryFunctorHolder), so it should be all good!

[dcoeurjo]

Thanks @rolanddenis . Merging