On Tuesday, January 15, 2002, at 07:38 PM, Hans Aberg wrote:
>
> Here, the action $1 | $3 would check the types of $1 and $3,
> and if they
> are combinable into a Boolean value it would do so; otherwise, it would
> combine them into a list object. (Think on for example C++ operator
> function name overloading based on argument type.)
This language is very weakly typed. So I don't know at parse
time the type of a variable, or for that matter that it is a
variable... could just be an unquoted string.
also:
answer "hello" with true or false
has two buttons. So I couldn't do that even if I had type information.
>> From the theoretical point of view, we merely give up trying
>> to capture the
> language (specifically, the distinction between the two
> different "or"'s)
> using a context free grammar alone: If we would want the
> grammar to capture
> this construction, it would lead to an attribute grammar or something.
I believe HyperCard --- the reference implementation --- uses a
hand-written recursive descent parser. Or at least I've heard
rumors to the effect. So I get to hold out some hope.
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