Re: Pointers to "why C behaves like that ?"

Roman Shaposhnick wrote:
> On 24 Nov 2002 18:38:19 -0500, Joachim Durchholz wrote:
>> Hindley-Milner typing is simple and efficient.
>
> But I suppose they require all pieces of code that has anything
> to do with "a" to be available at once.


This is correct insofar as type information can flow across subroutine
call boundaries.
However, it's useful even if it works just within a module - you can
omit almost all type annotations for local variables, for example. If
you have
      f (x: Real)
          local y
          y := x * x
you don't have to revisit the "local" declaration if you later discover
that the parameter of f should have been Numeric.
Or you can change the result type of a function.


Type inference will also help when importing modules.


When exporting from a module, type inference will give the most general
type that's consistent with the internal implementation. This type may
be more general than intended; for this reason, functions exported from
a module tend to have a type annotation.


> So, what I'm really saying is, that while dynamic typing is great
> in theory, I have yet to see a nice practical implementation,
> suitable for big software projects.


Take a look at Haskell. It's nice and practical, and IIRC it's already
being used for big projects.


Regards,
Joachim

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