[CCC DEV] Interfaces within "Plumbing"

[Steve Pretty]

A question has been bugging me about the design architecture of the 
plumbing library.

The library uses two  forms of protocol for communications between its 
"building blocks"  There is:

LEVEL - a user defined type with defined literals HIGH and LOW
SIGNAL

If you take the switch example from the plumbing book, it works like:

digital.input --[LEVEL]--> debounce --[LEVEL]--> level.to.signal 
--[SIGNAL]--> pin.toggle (converts back to LEVEL internally)

I am curious to understand the thinking behind creating and using these 
two different interfaces.  To my mind it creates a number of difficulties:

* Restricts inter connectivity of the blocks
* Requires adapter blocks to change between the two message types
* When working with SIGNAL, there is a loss of information - it marks a 
change of state - but was it a leading edge or a trailing edge? sorting 
this out required careful and error prone initial condition seeding of 
the blocks that convert from SIGNAL to LEVEL.

I wonder if there is not a case for applying Occam's Razor here - 
eliminate both these entities and use the standard BOOL throughout?