Re: Expression-local variables and 'let'

Quoting Isaac Gouy <[email protected]>:

> > What's wrong with alike?
> 
> It's an adjective, in Nice we use it as a pronoun.

Worse, it is a language keyword which only makes sense for the Java
methods-inside-classes syntax, but supports a concept that Java doesn't support. 

> > And it's not like something terrible will happen if you mistake one
> > for the other, either while reading or while writing the code.
>  
> If that was the case then why have "let" at all? 
> Presumably we think it will help prevent errors.

You need "let" so that you can have type inference for local variables:
    let x = 5; // okay, infer x's type
    y = 5;     // error, y is undeclared
You also need "let" any time you would normally use "final" in Java for a
field/variable. But, it doesn't work for parameters (e.g. int f(final int x) {
... }).

> > While, to make a comparison, something "terrible" can happen if you
> > intend to implicitely override a method, but for some reason fail to
> 
> Yes, that would definitely be a mistake. The question is where to catch
> the mistake. It seems that in some circumstances the compiler will be
> able to detect this, and in others it won't. (I may have intended to
> override the method in a subtype, the method is already covered by
> supertype implementations.) 

We discussed this in the covariant return type thread. Like I said there, I
would prefer to explicitly say "I am declaring a new method" and then have
specializations be implicit. Overloading is just a special case of "I am
declaring a new method." I think the syntax I suggested was:

method int foo(int y);

Also, I proposed an explicit syntax for specializing a generic function declared
in another package that was analogous to the syntax for declaring a subclass of
a class (in another package).

- Brian




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