[Python-Dev] RE: PEP 285: Adding a bool type

[Andrew Koenig]

Guido> You've been staring at standards too much, haven't you?  The
Guido> difference between MUST and SHOULD isn't as clear-cut as most
Guido> standards people use them.

In the ISO standards world, ``must'' doesn't mean what you
probably think it does:

        should:    encouraged, but not required
        shall:     required
        must:      it is impossible for things to be otherwise

So, for example, one can imagine describing a function with a
Boolean parameter named x by saying something like:

        If x is true, the result shall be foo.
        Otherwise, x must be false, and the result shall be bar.

-- 
Andrew Koenig, ark at research.att.com, http://www.research.att.com/info/ark