Syntactic Sugar In Lua

xrns · August 25, 2011, 12:41pm

this thread aims to collect all the so called “syntactic sugar” in Lua, in order to get an overview and possibly also sort out confusion

here’s a fresh example from the official Lua manual, discussing tables:

To represent records, you use the field name as an index. Lua supports this representation by providing a.name as syntactic sugar for a[“name”].
So, we could write the last lines of the previous example in a cleanlier manner as
  
 a.x = 10 -- same as a["x"] = 10  
 print(a.x) -- same as print(a["x"])  
 print(a.y) -- same as print(a["y"])  
  
For Lua, the two forms are equivalent and can be intermixed freely; but for a human reader, each form may signal a different intention.
A common mistake for beginners is to confuse a.x with a. The first form represents a[“x”], that is, a table indexed by the string “x”.
The second form is a table indexed by the value of the variable x. See the difference:
  
 a = {}  
 x = "y"  
 a[x] = 10 -- put 10 in field "y"  
 print(a[x]) --> 10 -- value of field "y"  
 print(a.x) --> nil -- value of field "x" (undefined)  
 print(a.y) --> 10 -- value of field "y"  
  

to be continued…