Words scoping: when another function nested within a function, the function can access local variables for external functions, such feature word is called scoping
table.sort (names, functin (n1, n2)
return Grades [n1]> Grades [N2]
End)
// anonymous functions can access the interior of the external function n1, n2
The first class values: lua which is a function value, he can present variable, as a function of parameters, as a return value
Test function ()
local I = 0
return function ()
I ++
...
End
End
// the return value as a function, also called I where outside the local variables is in lua upvalue
Closure: a function of internal plus external local variable (an upvalue) held by the external function external function (that is, plant) generated by calling an instance of function comprising
Closure Composition: upvalue + internal + external function function external functions created (closure function)
Example:
Test function ()
local I = 0
return function () // tailcall
I + =. 1
return I
End
End
C1 = Test ()
C2 = Test () // C1, C2 is built in the same function, the same local variable the above two different instances of different closures
// closure of upvalue independently, a call test () will produce a new closure
Print (C1 ()) ->. 1
Print (C1 ()) - -> each invocation repeated calls 2 // remember the last value of the call, that is i = 1 has a
print (c2 ()) -> 1 // different closures so upvalue different
print (c2 ( )) -> 2
The use of closures in the iterator: iterator needs to hold the last call and the call of a successful state, just use a closure mechanism can be implemented
:( create iterators must pay attention to the iterator just a builder, and he himself without circulation)
list_iter function (T)
local I = 0
local = n-table.getn (T)
return function ()
I = I +. 1
IF I <= n-return the then T [I] End
End
End
// list_iter here is a plant, each call will generate a new closure of the inner closure includes an upvalue (T, I, n-)
// so that each function call of the closure once the closure so generated will be based on a state of recording, and return to list next
Using an iterator: