Reserved tokens

[Till Mossakowski <till@informatik.uni-bremen.de>]

Dear Peter,

>However, perhaps "->" and "->?" should be reserved to avoid problems
>with parsing arising in a higher-order extension of CASL (where the
>distinction between SORT and TERM may disappear).  The question is
>then whether "*" should be reserved too - I hope not!  In fact I'd
>prefer to regard all of "->", "->?" and "*" as ordinary tokens usable
>as infix operators (but getting a predefined interpretation when
>applied to types in HO-CASL).
>
>Bernd, Till, et al.: please correct me if there are problems with the
>above. 

I have discussed the point with Bernd.
We agree that it is desirable to have  all of "->", "->?" and "*" as 
ordinary tokens usable as infix operators (this holds especially for "*").
We do not see problems with the HO extension.
If types do not contain terms, * is just a binary infix type
constructor. If types may depend on terms, there may be a difficulty
in recognizing the type/term frontier at (even context-sensitive)
parsing time - but this could be done during static analysis without
(forseen) problems.

By the way: the HO extension that we propose will distinguish
between ->? and -> ? (they have different semantics).

Greetings,
Till