Some interesting Lua code test
When I read the book <the ruby way>, I get some interesting code that need to run in Lua. (I will test following code in Lua5.14 for windows package.)
1: print( 5 % 3)
2: print( -5 % 3)
3: print( 5 % -3)
4: print(-5 % -3)
The result will be 2, 1, -1, -2.
1: if not nil then
2: print("not nil")
3: end
4:
5: if not false then
6: print("not false")
7: end
8:
9: if 0 then
10: print("0")
11: end
12:
13: if "" then
14: print("empty string")
15: end
The result will be "not nil", "not false", "0", "empty string", in Lua, only nil and false will be FALSE in condition checking.
1: for i = 1, 5 do
2: print(i)
3: i = i + 5
4: print(i)
5: print("")
6: end
OK, the result will be 1 6, 2 7, 3 8, 4 9, 5 10, you could see the index variable "i" is not changed for the for-loop, and you could assign new value (i=i+5) to it in the for range, but it will restore back to the loop index value again.
1: local x, y = {}
2: print(x)
3: print(y)
4:
5: y = x
6: print(y)
7: table.insert(y, "aa")
8: print(x[1])
It will print like "table: 003CACB0" "nil" "table: 003CACB0" "aa".
Two thing need to note, local x, y = {} will only initialize the "x". Another is the y will have same address with x if x is a table, and insert to table y will cause x changes too. It seems like in c or c++ only copy the pointer address, not copy the value with the pointer.
Tags : lua