Why is an empty lambda body not allowed?

[Tobias Brandt]

Hi,

it seems to be illegal to write

    (lambda ())

I would have expected this to evaluate to a procedure returning unspecified.

On the other hand, the following are all valid

    (begin)

    (define x (begin))

    (lambda () x)

but

    (lambda () (begin))

is not.

Why is that?

Cheers,

Tobias