In some functional programming languages, they can pattern match a function based on its parameters. Similar to function overloading. Will Python Pattern Matching do something similar to functions?
If calling a function doesn't match any of the cases and catch-all case is not present, then some sort of new or exisiting Exception needs to be raised.
Type annotations can be used (for the parameters, they may be redundant, but for the return, they can be useful). The Return annotation comes right after the guard.
See theortical example below.
class Point:
def __init__(self, pos):
self.pos = pos
def write(self, msg):
return f"writing {msg}"
match def f:
case (float(x) | int(x), float(y) | int(y)) if x > 0 -> int:
return round(x + y)
# f(3.4, 7) => 10
case (int(x) | float(x)):
return round(2 * x)
# f(8) => 16
case (0):
return 0
# f(0) => 0
case (0, 0):
return "Origin"
# f(0, 0) => "Origin"
case ([int(x) | float(x), int(y) | float(y)], int(z) | float(z)):
return x + y + z
# f((5, 2.5), 2.5) => 10
case (
(Point(pos=(int(x), int(y)))) as point,
*_,
message=str(msg),
**_,
) if x > 0 and y > 0:
txt = point.write(msg)
res = x + y
return res, txt
# point = Point([1, 9])
# f(point, message="Hello") => 10, "writing Hello"
case (*_, **_):
return "Catch_All"
## which can be shortened to...
case _:
return "Catch_All"
#f(1, 3, 4, 5) => “Catch_All"