Semantic portal
Lexical closures
A closure is a function object that has access to variables in its lexical scope, even when the function is used outside of its original scope.
/// Returns a function that adds [addBy] to the function's argument.
Function makeAdder(num addBy) {
return (num i) => addBy + i;
}
void main() {
// Create a function that adds 2.
var add2 = makeAdder(2);
// Create a function that adds 4.
var add4 = makeAdder(4);
assert(add2(3) == 5);
assert(add4(3) == 7);
}Can close over variables defined in surrounding scopes.