Proper pattern matching

[WilliamRagstad]

Currently the = operator is more of a naive "statementy" expression verifying that the variable in an assignment isn't already defined in the global scope. This has also caused problems such as #1.

The features suggested in this issue is to move towards the functional idea of the = operator. Meaning allowing LHS and RHS to be swapped at will (symmetric property), but most importantly the implementation must be compatible with #11.

The desired functionality would be:

• Comparison

  a = 10 # true, side-effect: a is defined
  a = 10 # true, no side-effect
  5 * 2 = a # true, no side-effect
  b = 80
  c = b / 2 = a * 4 # true, side-effect: c is defined
  3.1415926535 = c / a # false (nice try tho)

• Variable scope shadowing Variable scope shadowing #2

  a = 10 # true, side-effect: a is defined in global scope
  a = 42 # false
  {
    a = 42 # true, side-effect: a is defined in local scope, shadow parent scope
  }

• Destructuring with recursive pattern matching

  [a, 10, b | [(42, c), tail]] = [-2, 10, 25, (42, "Hello"), 0]
  # a = -2, b = 25, c = "Hello" and tail = [0] 

• Reverse concatination

  firstname + " " + lastname = "John Doe"
  # firstname = "John" and lastname = "Doe"

• Basic reverse aritmetics (for non-ambigious, single "answer" expressions. Not meaning + life = 42)

  a = 1000
  b ^ 3 = a
  # b = 10

More suggestions may come, this list is not complete.