Bidirectional binding

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In addition to corrections to local variable binding the next update of the JavaFX interpreter will include extended bidirectional binding, including of logical negation, unary minus, arithmetic, and sequence indexing. Here's a JavaFXPad example you can try out:

// logical negation
var a = true;
var b = bind not a;
assert b == false;
b = true;
assert a == false; // passes

// arithmetic
var x = 10;
var y = bind -x + 100;
assert y == 90;
y = 40;
assert x == 60; // passes

// sequence elements
var seq = [1, 2, 3];
var elem1 = bind seq[1];
elem1 = 500;
assert seq == [1, 500, 3]; // passes
delete seq[1];
assert elem1 == 3; // passes
insert 0 as first into seq;
assert elem1 == 1; // passes
var value = bind elem1;
value = 999;
assert seq == [0, 999, 3]; // passes