higher order functions - compilation question

> Hi,
>
> Aren't
> def bar(): Long = 3
> and
> def bar: Long = 3
> equivalent?

Seems, they are not, from a type perspective:

scala> def first:Long = 3
first: Long

No parens.

scala> def second():Long = 3
second: ()Long

parens as part of the type.

> Why does the following code snippet compile with a type
> mismatch error (found Long, required () => Long)?
>
> def foo(f: () => Long) = f
> def bar: Long = 3
> foo(bar)

In the last line's expression, 'bar' is evaluated first,
resulting in a Long, which does not match the type of foo's param.

Use by-name parameter to solve this, instead of function type:

scala> def foo (f: => Long ) { println ( f ) }
foo: (=> Long)Unit

----> OK now:

scala> foo(first)
3

----> And even:

scala> foo(second)
3

See PiS page 206 for details

The solution with
def bar(): Long = 3
seems to work, as the type of the expression 'bar' (i.e.: ()=>Long)
matches exactly the expected type of foo's param, so the system assumes
that bar shall not be evaluated first.

KR
Det