The ":" is a binary operator used in expressions, it is bound to a specific function that creates a binding between to object, that binding being a new object that can be used to perform a function call in a special way (which modifies the list of operands by prepending the first parameter of the binding). The ":" can be used between any pair of objects.
No, that's not true. That's how it works in Python, but in Lua it is NOT a binary operator but rather a part of a ternary function call operator.
But when you parse it, that's what happens: you have to take care of the associativity.
It's just that for now there are additional limitations on the second operand (which can only be a single identifier, limiting its usability, much like "." is limited unless rewritten as "[string _expression_]". The third operand(s) (with or without parentheses around them) do not play any syntaxic role for recognizing ":".
And I don't know if there's any future plan to allow the syntax "a:[string _expression_]()" or allow "a:b" alone or "a:[string _expression_]()" to be a new "functor" object type, i.e. without opening parentheses after it, to generalize the concept of function calls. Arbitrary example showing all cases of use:
local functor = a:max or a
x = functor() + functor c + functor(c + 1, x -2)
But that's not what I propose. I'm just limiting myself to the syntactic role (binary associativity) only, rather than semantic (only operators in expressions) which just comes next.
