In Mathematica, you might do this as (roughly):
rules = {
{x_, y_, z_} :> {x, y, z},
{x_, y_} :> {x, y, 0.0},
x_ :> {x, 0.0, 0.0}
}
process[Replace[obj, rules]]
Whatever you think of the particular syntax:
The ability to declare resuable rules seems good.
Thinking of replacement functionally seems good.
fwiw, Alan Isaac
On 11/17/2020 5:02 AM, Steven D'Aprano wrote:
On Tue, Nov 17, 2020 at 08:49:28AM +0100, Marco Sulla wrote:
PS: pattern matching, for a mere mortal like me, seems to be something very
exotical.
Have you ever written code that looks like this?
if isinstance(obj, tuple) and len(obj) ==3:
x, y, z = obj
elif isinstance(obj, tuple) and len(obj) == 2:
x, y = obj
z = 0.0
elif isinstance(obj, float):
x = obj
y = z = 0.0
else:
raise ValueError
process(x, y, z)
That's pattern matching.
match obj:
case x, y, z:
pass
case x, y:
z = 0.0
case x if isinstance(x, float):
y = z = 0.0
case _:
raise ValueError
process(x, y, z)
There may be cleaner or alternative ways to write this as a match
statement, I'm still learning pattern matching idioms myself. But in a
nutshell, they simplify what would otherwise look like a long,
repetitive chain of if, isinstance, sequence unpacking, etc.
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