Library implementation for pattern matching

[Idan Arye via Digitalmars-d]

On Monday, 25 August 2014 at 22:35:08 UTC, Dicebot wrote:
> Don't have time to comment in details but wanted to warn about 
> one thing : don't over-engineer. There is only limited value in 
> a smart utility if its usage pattern can't be immediately 
> recognized by a new developer.

Well, what I had in mind is more complex than 
`predSwitch`/`castSwitch`/`regexSwitch`, but not *that* complex. 
I want to support syntax like:

uint multiplyTuple(Tuple(int, int) operands){
     return operands.patternMatch!(
         (Constrainted!(uint, "==", 0), uint _) => 0,
         (Constrainted!(uint, "==", 1), uint b) => b,
         (a, uint b) => b + multiplyTuple(tuple(a - 1, b)),
     )();
}