[Python-ideas] Match statement brainstorm

Greg Ewing greg.ewing at canterbury.ac.nz
Thu May 26 19:10:08 EDT 2016

Nikolaus Rath wrote:
> I think its much
> better to embed the target variables in the pattern - we just need a way
> to mark them as such.
> maybe we could use $?

I'd like to suggest using '?' instead. It looks more pattern-
matchy to me.

Trying to come up with some real-looking examples:

    switch obj:
       case Point(?x, ?y):
          print("Point at", x, y)
       case Line(start = ?p1, end = ?p2, width = ?w):
          print("Line from", p1, "to", p2, "with width", w)
       case Intersection(?obj1, ?obj2):
          print("Intersection of", obj1, "and", obj2)

    switch command:
       case ("frobulate", ?inp, ?out):
          print("Frobulating", inp", "to give", out)
       case ("frobulate", "-v", ?inp, ?out):
          print("Frobulating", inp, "verbosely to give", out)
       case ("xyzzy", ?)
          print("Xyzzying not implemented, sorry.")
          print("Couldn't grok your command, master.")

Here I've also used '?' without a following name as a
"don't care" marker.


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