Increment to Lua

Question

I play a little with Lua.

I came across the following piece of code that has unexpected behavior:

a = 3; b = 5; c = a-- * b++; // some computation print(a, b, c); 

Lua launches the program without any errors, but does not print 2 6 15 as expected. Why?

Answer 1

-- launches one line comment , for example # or // in other languages.

So this is equivalent to:

 a = 3; b = 5; c = a 

Answer 2

LUA does not increase or decrease with ++ and -- . -- will start a comment instead.

Answer 3

If you want 2 6 15 as output, try this code:

 a = 3 b = 5 c = a * b a = a - 1 b = b + 1 print(a, b, c) 

Answer 4

It will give

3 5 3

because the 3rd row will be evaluated as c = a

why? because in lua comments start with -. Therefore c = a-- * b ++; // calculation

estimated as two parts:

• expression: c = a
• comment: * b ++; //// some calculations