Re: Soft Types System Proposal

[Philippe Lhoste <PhiLho@...>]

Mark Hamburg wrote:

> In my experience with Lua, type errors are relatively rare, but typing
> errors are common. What those seem to need are an easy way to detect:
>
> * Undefined variables. The various Lua lints detect this by looking for
> unexpected global access. The language could probably become friendlier
> about this though that would have to be balanced against keeping the
> language friendly toward incremental compilation. Perhaps "new" globals
> should only be allowed at the top level of a chunk.

That's funny how some topics bubble up (?) frequently on this mailing 
list... Depending on the point of view, that may mean:
- that users express a deep need that must be addressed;
- that Lua is deeply incompatible with some ways of thinking, and users 
either should get used to this way, or use another language.

This proposal is quite close of the frequent request of "local by 
default". It can't be accepted "as is", because it would break some scripts.
Don't forget that Lua is initially a configuration language, used to 
express dynamically data structures. With your proposal, some constructs 
would be impossible.
I suppose this could be addressed by a "global" keyword.

Anyway, this have been proposed many time, and always rejected by Lua 
authors, either because of compatibility, or because of fundamental 
philosophy of Lua, or some other reason I forgot...

Maybe this topic can go in the Lua FAQ: http://lua-users.org/wiki/LuaFaq
There is already the "How can access of undefined variables be caught in 
Lua?" question, but this could be expanded a bit more.

A "Lua Philosophy" entry in the Wiki may clear these questions definitively?

"Why Lua variables are global by default?"
"Why this will no change?"
"Why there is nothing like Visual Basic's 'Option Explicit' to catch 
undefined variable uses?" (because it is simple to do it already: in the 
Wiki)
"Why does Lua lack the += operator, etc.?" (in the Wiki)
"Why there is no xxx feature like in my favorite language (switch, 
continue, etc.)" (there should be the workarounds as seen on the mailing 
list)
"etc."

Most of these questions, and the related answers, are on the mailing 
list archive. If a good soul, with lot of time on his hands, and a good 
motivation, could search these and copy them on the Wiki, that would be 
nice.

--
Philippe Lhoste
--  (near) Paris -- France
--  Professional programmer and amateur artist
--  http://Phi.Lho.free.fr
--  --  --  --  --  --  --  --  --  --  --  --