Suggest class name in factory instantiation

[gf712]

Intro

Instead of using directly the classes from C++, we use factories (see here). So for example in Python, instead of

import shogun as sg
kernel = sg.GaussianKernel()

we have

import shogun as sg
kernel = sg.kernel("GaussianKernel")

To find out what all possible names you can have a look at src/shogun/base/class_list.cpp, after compiling shogun.
The issue with this approach is that it is easy to mistype a name, e.g. "Gaussiankernel", and after several hours of writing code these errors might happen more frequently and not so obvious to debug.
Right now you would get a message like this:

SystemError: [ERROR] In file /home/gil/shogun/src/shogun/base/class_list.h line 51: Class Gaussiankernel with primitive type SGOBJECT does not exist.

The task

Catch these errors with SWIG, for example in src/interfaces/shogun.i and try to find out what the user actually meant. This should be written in C++, which would make it accessible to all languages.

Some pointers

• A good approach would be to calculate the distance between the string the user passed and all the classes in shogun
• All classes in shogun that are exposed via factories can be accessed with shogun::available_objects()
• A good distance metric for this is levenshtein, which is not implemented anywhere in shogun, but it is pretty straighforward (see here).
• Check Suggest class names if class name not found #4473, it has a Python implementation of this

[karlnapf]

Note: this should not be implemented in a standard c++ shogun source, but in the swig extension. E.g. see https://github.com/shogun-toolbox/shogun/blob/develop/src/interfaces/swig/shogun.i

EDIT: Or, since string distances are actually kinda useful, this can be added to shogun itself in the same way as CHammingWordDistance. Then shogun would use itself for generating error messages 😎