From Beginning Lua Programming:
"When a function uses a variable that is local to a containing scope ... that variable is called an external local variable or an upvalue. ... A function that has one or more upvalues is called a closure." In the following code N is an upvalue.
> function MakeLessThan(N)
>> return function (X)
>> return X < N
>> end
> end
> LessThanFive = MakeLessThan(5)
> print (LessThanFive(4))
true
You can also call a function directly, without giving it a name.
> print (MakeLessThan(5) (4))
true
1 comment:
"A local value used by an inner function is called an upvalue." Still trying to understand this concept.
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