Syntax...

[Vladimir Kirichenko]

Neal Gafter wrote:
> On Sat, Nov 21, 2009 at 10:19 AM, Vladimir Kirichenko
> <vladimir.kirichenko at gmail.com <mailto:vladimir.kirichenko at gmail.com>>
> wrote:
> 
>            /AnonymousLambda/:
>                    fun /TypeSpec/ => /Body/
>            /TypeSpec/:
>                    /Type/? /ParamsSpec/? /ThrowsSpec/?
>            /ParamsSpec/:
>                    ( /Param/+ )
>            /Param/:
>                    /Type/ ID
>            /ThrowsSpec/:
>                    throws /ExceptionType/+
>            /Body/:
>                    /Expression/ | { /StatementList/ }
> 
>     The return type, params and throws declared optional to reduce
>     unnecessary "empty" constructs.
> 
> ...
> 
>     EBNF:
> 
>            /Function/:
>                    fun /TypeSpec/ /Assignment/?
>            /Assignment/:
>                    = /AnonymousLambda/
>            /TypeSpec/:
>                    /Type/? ID /ParamsSpec/? /ThrowsSpec/?
>            /ParamsSpec/:
>                    ( /Type/+ )
>            /ThrowsSpec/:
>                    throws /ExceptionType/+
> 
> ...
> 
>     EBNF:
> 
>            /Function/:
>                    fun /TypeSpec/ => /Body/
>            /TypeSpec/:
>                    /Type/? ID /ParamsSpec/? /ThrowsSpec/?
>            /ParamsSpec/:
>                    ( /Param/+ )
>            /Param/:
>                    /Type/ ID
>            /ThrowsSpec/:
>                    throws /ExceptionType/+
>            /Body/:
>                     /Expression/ | { /StatementList/ }
> 

Sorry for confusion - it's 3 differened EBNFs - haven't synced them.

> This is all very confusing.  From /Function/ I derive
> 
> using
>     /Function/:
>                fun /TypeSpec/ /Assignment/?
> 
> we get
> 
> fun /TypeSpec/ /Assignment/
> 
> using
>        /TypeSpec/:
>                /Type/? /ParamsSpec/? /ThrowsSpec/?

It's wrong TypeSpec. In /Function/ it's slightly different:

            /TypeSpec/:
                    /Type/? ID /ParamsSpec/? /ThrowsSpec/?

> and taking all the optional parts to be empty, we get
> 
> fun /Assignment/

fun ID /Assignment/


> Then using
>        /Assignment/:
>                = /AnonymousLambda/
> 
> this results in
> 
> fun = /AnonymousLambda/

fun ID = /AnonymousLambda/

> Then using
>        /AnonymousLambda/:
>                fun /TypeSpec/ => /Body/
> 
> this becomes
> fun = fun /TypeSpec/ => /Body/

fun ID = fun /TypeSpec/ => /Body/

> Again, taking /TypeSpec/ to be empty, as before, and using
>        /Body/:
>                /Expression/ | { /StatementList/ }
> 
> we finally get
> 
> fun = fun => 3

fun ID = fun => 3

> I just have no idea what it is all supposed to mean.  Is this a
> declaration?  A statement?  An expression?  Is it supposed to define
> something?

so it's a declaration of identifier ID of declared type "fun void ()"
and type mismatch compiler error "expected: void but found: int".



-- 
Best Regards,
Vladimir Kirichenko

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