On Sun, 2006-09-10 at 20:07 -0400, Peter Tanski wrote:
>
> Thanks for the insight. Felix must also perform a little semantic
> analysis while parsing
It does. Well not 'semantic' analysis, but it does analyse
the syntax before chosing which AST node to emit. For example
endl;
endl ();
are *syntactically* equivalent. This isn't a type thing, rather:
match expr with
| apply(a,b) -> apply(a,b)
| x -> apply(x,())
is used. Thus, the transform also applies to macros.
This transformation isn't "sound" in some sense,
because there's no way to write 'x' and have 'x'
come out: it relies on the fact that the statement:
expr;
is never well formed unless it is a procedure application.
The transform could break if this invariant were invalidated
by some other change.
> because function names (though prefixed with 'fun') and certain
> keywords, such as 'list' and 'typeclass' are appended with
> square-bracketed material:
>
>
> fun f[T1,T2]
> typeclass[T1,T2]
> list[int]
>
list isn't a keyword :)
unqualified names are encoded by
`AST_name (sr,name,ts)
where
sr is the line/column position
name is a string of the identifier
ts is a list of types
Thus
fred
is actually encoded in Ocaml as
`AST_name (some_loc, "fred",[])
where [] is an empty list. This is an atomic form in expressions:
x[int,long]
is an atom. ALL names can be subscripted, everything is
first order polymorphic.
Sometimes the parser won't accept subscripts, and sometimes
the subscripts have to be an empty list, but the AST term
always allows them (for names in expressions). Definitions
are different.
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