Difference between revisions of "Nil"
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If a function call returns no results and yet it is assigned to a variable, that variable is still [[nil]]. If a function returns fewer results than available assignment variables, the extra variables are set to nil. | If a function call returns no results and yet it is assigned to a variable, that variable is still [[nil]]. If a function returns fewer results than available assignment variables, the extra variables are set to nil. | ||
| − | local f = function() return 1,2 end | + | local f = function() return 1,2 end |
| − | + | local a,b,c = 1,1,1 | |
| − | + | a,b,c = f() | |
| − | + | print(type(c)) | |
| + | if c == nil then print('the value of c was 1, but now it's nil!') | ||
| − | + | --> 'nil' | |
| + | --> the value of c was 1, but now it's nil! | ||
| + | |||
| + | Confusingly, nil can be used as a return value. | ||
| + | |||
| + | local f = function return nil end | ||
| + | local a,b,c = 1,1,1 | ||
| + | a,b,c = f() | ||
| + | print(type(a)) | ||
| + | |||
| + | --> 'nil' | ||
| + | |||
| + | And also as a parameter. | ||
| + | |||
| + | local f = function(any) print(type(any)) end | ||
| + | f() | ||
| + | f(nil) | ||
| + | |||
| + | --> 'nil' | ||
| + | --> 'nil' | ||
| + | |||
| + | == See Also == | ||
| + | |||
| + | * [[...]] | ||
| + | |||
| + | * [[type]] | ||
| + | |||
| + | * [[tuple]] | ||
Latest revision as of 18:58, 1 November 2010
nil is a lua keyword and valid value and specifies something that does not exist.
local a = 1 a = a + b
--> 'Error: attempt to perform arithmetic on global 'b' (a nil value)'
If no value has been assigned to a variable, then it is of type 'nil'.
local a print(type(a))
--> 'nil'
If a function call returns no results and yet it is assigned to a variable, that variable is still nil. If a function returns fewer results than available assignment variables, the extra variables are set to nil.
local f = function() return 1,2 end
local a,b,c = 1,1,1
a,b,c = f()
print(type(c))
if c == nil then print('the value of c was 1, but now it's nil!')
--> 'nil' --> the value of c was 1, but now it's nil!
Confusingly, nil can be used as a return value.
local f = function return nil end local a,b,c = 1,1,1 a,b,c = f() print(type(a))
--> 'nil'
And also as a parameter.
local f = function(any) print(type(any)) end f() f(nil)
--> 'nil' --> 'nil'
