Re: Soft Types System Proposal

[Asger Ottar Alstrup <aalstrup@...>]

Regarding the type system in Javascript: That type system is similar to 
what is proposed for Lua: They have an "Any" type, which they call 
Object, they use Pascal like syntax: "var x:Integer; function 
foo(x:Number):Number {return x;}", defining types is optional, and 
adding type annotations does not change the meaning of the program.

It is different in that:

1) they allow type expressions such that you can use a variable as a 
type in the syntax (with the meaning that type intended is the type of 
the variable),

2) they have many more types in the language (including a "Never" type 
for no values, and "Void" for functions that do not return a useful value),

3) they define a range of implicit coercions

4) they provide syntax for explicit coercions.

Regarding 1, I think that is a mistake.

Regarding 2, a "Void" type might be useful.

Regarding 3, the only implicit coercion in the proposal is that 
everything can convert to the "Any" type. The others are not relevant in 
Lua, given the few basic built-in types.

Regarding 4, this can be expressed as functions that take an any 
parameter and return the required type, so no need for special syntax.

Regards,
Asger Ottar Alstrup