Pattern

Matches exp against the given pattern pat. Raises Pattern::MatchFailedError if matching fails.

a, b, c, d = nil, nil, nil, nil
Pattern.match!([1, [2, 3], 4], {a, {b, __splat(c)}, d})
values = {a, b, c, d} # => {1, 2, [3], 4}
typeof(values)        # => Tuple(Array(Int32) | Int32, Int32, Array(Int32), Array(Int32) | Int32)

Pattern.match!([1, 2], {a, b, c}) # Pattern::MatchFailedError: matching against {a, b, c} failed

The code below shall be equivalent to above:

[1, [2, 3], 4] ~> {a, {b, *c}, d}
values = {a, b, c, d} # => {1, 2, [3], 4}
typeof(values)        # => Tuple(Array(Int32) | Int32, Int32, Array(Int32), Array(Int32) | Int32)
[1, 2] ~> {a, b, c}   # Pattern::MatchFailedError

Attempts to match exp against the given pattern pat. Returns true if matching succeeds, false if matching fails.

Due to language limitations, using this macro in a condition does not fully constrain the types of the bound variables in the pattern; use Pattern.try_match instead.

a, b, c, d = nil, nil, nil, nil
if Pattern.matches?([1, [2, 3], 4], {a, {b, __splat(c)}, d})
  values = {a, b, c, d} # => {1, 2, [3], 4}
  typeof(values)        # => Tuple(Array(Int32) | Int32 | Nil, Int32 | Nil, Array(Int32) | Nil, Array(Int32) | Int32 | Nil)
end

The code below shall be equivalent to above:

if [1, [2, 3], 4] ~>? {a, {b, *c}, d}
  values = {a, b, c, d} # => {1, 2, [3], 4}
  typeof(values)        # => Tuple(Array(Int32) | Int32, Int32, Array(Int32), Array(Int32) | Int32)
else
  values = {a, b, c, d} # => {nil, nil, nil, nil}
  typeof(values)        # => Tuple(Nil, Nil, Nil, Nil)
end

Attempts to match exp against the given pattern pat. Invokes the block body if matching succeeds. Returns nil.

This method is for testing purposes only. Language support for pattern matching should implement proper flow typing for successful matches.

a, b, c, d = nil, nil, nil, nil
Pattern.try_match([1, [2, 3], 4], {a, {b, __splat(c)}, d}) do
  values = {a, b, c, d} # => {1, 2, [3], 4}
  typeof(values)        # => Tuple(Array(Int32) | Int32, Int32, Array(Int32), Array(Int32) | Int32)
end