Re: Static typing in Lua

[Gavin Wraith <gavin@...>]

In message
<89d273ba0607262003x2f2ffd4el98b7bccc715ccaf5@mail.gmail.com> you wrote:


> I'm trying to figure if it would be possible to add static (compile
> time) typing to Lua easily, either by adding a library or by modifying
> the language parser itself. Has anyone already looked into it and
> found something interesting ? Is the Lua core designed to allow such
> modification ? An alternative would be to add a kind of preprocessor
> to Lua. I read somewhere that there is a Lua parser written in Lua.
> Would it be capable of doing such preprocessing ?
> 
> Static typing enforce some level of code correcteness and that's the
> aspect of it that I'm looking for.

I have been thinking about this a little. The function

 the = function (s,x)
        if assert(type(x) == s) then return x end
       end

which is useful for superficial typechecking, suggests the use
of identity functions with side effects which create type
information.

I think nil has to have every type.

As to what constitutes a type perhaps one should go through
all the code in the VM looking for branching decisions, and
make an abstract definition of "a type relevant to a given
VM operation" as something that resolves branches for that
op. Or am I being silly? This is a notion analyzed from the
point of view of the cpu rather than the user, so to speak,
and so may not be quite what you mean.

-- 
Gavin Wraith (gavin@wra1th.plus.com)
Home page: http://www.wra1th.plus.com/