laiboonh
Parameter pattern matching
Can someone explain to me how parameter pattern matching works exactly?
def foo({a,b}) do
...
end
foo({1,2})
Pattern matching that happens: {a,b} = {1,2}
def equal(a,a), do: true
equal(1,1)
Pattern matching that happens?
I was wondering because if it happens like a=1 and then a=1 then equal(1,2) would have matched fine because a=1 and then a=2 is totally legal.
Marked As Solved
dom
During compilation
def equal(a,a), do: true
is basically rewritten to
def equal(a,b) when a === b, do: true
Both these functions compile to the exact same bytecode.
Also Liked
dom
It’s explained here: https://elixir-lang.org/getting-started/pattern-matching.html
If a variable is mentioned more than once in a pattern, all references should bind to the same pattern:
iex> {x, x} = {1, 1}
{1, 1}
iex> {x, x} = {1, 2}
** (MatchError) no match of right hand side value: {1, 2}
idi527
a=1 and then a=2 is totally legal
It is not actually. The assignment happens once (a=1), and a=2 would mean 1=2 which doesn’t match.
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