Changes:
- Eff has become EffM, parameterised over (m : Type -> Type), which will
allow us to introduce new effects later, though not currently used
- Eff itself is now a collection of type synonyms which build an EffM.
It can take either one list of effects, a list of input and output
effects, or a list of effects and a function to compute output
effects; disambiguated by context
- EffT is as Eff, but takes the underlying 'm'
- Added 'sig' function for giving effect signatures.
All of the above mean we no longer need the {} syntactic sugar, though
it's still there. Old effect programs (should!) work with no or minimal
changes.
The changes are as follows:
+ `print` is for putting showable things to STDOUT.
+ `printLn` is for putting showable things to STDOUT with a new line
+ `putCharLn` for putting a single character to STDOUT, with a new line.
Effects has been updated accordingly.
They can be imported from the modules Data.Fin, Data.Vect, and Data.So
respectively.
The general thinking here is that not every program is going to need
these, and they are often used especially by newcomers in place of
something more appropriate. Also, all of them are useful for teaching,
which means it is instructive for tutorials to introduce them and have
people implement them themselves.
