The 3rd map/reduce api style is buggy.
Fix include guards.
Try another map/reduce API design.
Add mr2, the 2nd map/reduce coding style.
Rename typename wordcount_job to job_type.
Move job/mapper/reducer to namespace swk::mr1.
I'm going to try different client API styles.
Now the computation of reducer part is done, too.
Correct reducer type parameters.
Rename ctx to mc, which means mapper context.
Mapper can run now.
Fix 'inaccess type' compilation problem.
Add the initial libswk library.