[Python-Dev] Re: switch statement

[Michael Chermside]

Andrew McGregor writes:
> I can post an alternative, inspired by this bit of Haskell
    [...]
> The intent is that within the case, the bit before each : is a boolean
> expression, they're evaluated in order, and the following block is
> executed for the first one that evaluates to be True.

If we're going to be evaluating a series of booleans, then the One Proper
Format in Python is:

     if <bool-expr-1>:
         <suite-1>
     elif <bool-expr-2>:
         <suite-2>
     elif <bool-expr-3>:
         <suite-3>
     else:
         <default-suite>

When people speak of introducing a "switch" statement they are speaking
of a construct in which the decision of which branch to take requires
time proportional to something LESS than a linear function of the number
of branches (it's not O(n) in the number of branches).

Now the pattern matching is more interesting, but again, I'd need to
see a proposed syntax for Python before I could begin to consider it.
If I understand it properly, pattern matching in Haskell relies
primarily on Haskell's excellent typing system, which is absent in
Python.

-- Michael Chermside