Re: Why does lua interpreter need = in front of variables?

[Bradley Smith <gmane@...>]

Matthew Wilson wrote:
> I am learning lua after using python for the last few years.
>
> In the lua toplevel, why do I either have to either put a "=" in front
> of a variable?
>
> In python, the toplevel evaluates everything automatically:
>
>     $ python
>     Python 2.5.1 (r251:54863, May  2 2007, 16:56:35)
>     >>> 1 + 1
>     2
>     >>>
>
>     $ lua
>     Lua 5.1.2  Copyright (C) 1994-2007 Lua.org, PUC-Rio
>     > 1 + 1
>     stdin:1: unexpected symbol near '1'
>     > = 1 + 1
>     2
>     >
>
> I started thinking about this, and I wondered if maybe the "=" forces
> the toplevel to evaluate the object.
>
> I'm just curious, but this detail stumps me.

The input "1 + 1" is not a full statement. It is just an expression. The 
Lua interpreter parses and executes full statements. The input "= 1 + 1" 
is shorthand for "return 1 + 1" which is a full statement. In addition, 
Lua interactive mode allows a statement to be multiple lines. For example:

    >lua
    Lua 5.1.2  Copyright (C) 1994-2007 Lua.org, PUC-Rio
    > = 1 +
    >> 1
    2
    >