[Aldor-l] empty Generator?

[Ralf Hemmecke]

> However for your grnerator one, the algebra library exports a partialNext!
> function which allows to detect if g is empty:

Thank you for your quick answer, but I should have mentioned that I know 
about "next!" and "partialNext!".

But it does not help to make the following work. If I implement

empty?(g: Generator(Integer)): Boolean == failed? partialNext! g;

then

>> g: Generator Integer := generate yield 123;
>> b: Boolean empty? g;
>> l: List Integer := [g];

would give l=[] instead of l=[123].

So either there is a way supported by the compiler or it simply is not 
possible.

Of course I could define MyGenerator which is like a 
one-token-look-ahead stream, but then MyGenerator is different from 
Generator and it cannot be used in library functions that require Generator.

So my question was in fact, whether Generator is implemented as a 
one-token-look-ahead stream similar to TextReader. (Note that TextReader 
has a function "push!: (Charcater, %) -> ()" to push back one character.)

Ralf