Re: Is string always same as number? (the consistency of lua)

[Christian Tellefsen <christian.tellefsen@...>]

On 2/11/2011 12:46 PM, Alex Queiroz wrote:
>      Wrong. Strong typing means that, like in Ocaml, you cannot add
> integers to floating point numbers directly. Even in C, with its
> static type system, integers are silently promoted to floating point
> numbers in such a case.
Unfortunately, 'strong typing' isn't well defined, and means quite a lot 
of different things. A language can be strongly typed in some ways while 
simultaneously weakly typed in other ways.

Compile time type checks, lack of automatic conversion, no type 
conversion, well defined type behavior, detection of type errors, no 
access to underlying representation, etc., are examples of strong typing.

In general, the earlier you can detect a type error, the less chance 
there is of you getting surprised by type errors, and the more you can 
use the type system to detect, the stronger the typing is.

As far as I know, Lua is strongly typed in (at least) these ways:

* It has a type system.
* There is run time type checking (= dynamic typing).
* Typing errors are always detected and reported when they happen.
* You have no access to the underlying representation (no 
reinterpret_cast, for example).
* Each variable always contains a value with a particular type, and you 
can find out what it is.

And weakly typed in these ways:

* There is no compile time type checking (= static typing).
* It has some automatic type conversion.
* It has fairly coarse grained typing (one single numeric type)
* It has few types (8 or 9, depending on whether you think userdata and 
lightuserdata are the same type)
* It has no type modifiers (like const, for example).
* You can't create new types or new complex / compound types.

Cheers,
Christian Tellefsen