OK. I understood about common case. But may I at least look in compile time what fields the class have?
(define a (class object% (super-new) (field f1 f2 f3))) In runtime I can do (field-names (new a)). But in syntax `a' has no value. Even for struct one can have compile-time information fo accessors, but how to make it with classes?. Tue, 1 Apr 2014 11:10:09 -0400 от Matthias Felleisen <[email protected]>: > >There can't be: > >(define c-without-fields (class object% (super-new))) >(define c-with-a-field (class object% (super-new) (field [a 0]))) > >(define d (class (if (tuesday?) c-without-fields c-with-a-field) (super-new) >... a ...)) > >It is impossible to determine whether this module is closed i.e. a valid >program. > > > >On Apr 1, 2014, at 11:06 AM, Asumu Takikawa < [email protected] > wrote: > >> On 2014-04-01 13:43:55 +0400, Roman Klochkov wrote: >>> Is there a way to inherit all fields ? >>> >>> For example >>> >>> (define a (class object% (super-new) (field f1 f2 f3))) >>> >>> (define b (class a (super-new) (field f4 f5 f6))) >>> >>> (define c (class b (super-new) (inherit-field f1 f2 f3 f4 f5 f6))) >>> >>> How to avoid manual enumeration of all f1 ... f6? >> >> I don't think there is, because you don't always know what what fields >> your superclass will have. The `inherit-field` form gives you meaningful >> errors if your superclass turns out not to have the field to inherit, >> but it's not clear what to do for "all fields". >> >> Cheers, >> Asumu >> ____________________ >> Racket Users list: >> http://lists.racket-lang.org/users > -- Roman Klochkov ---------------------------------------------------------------------- -- Roman Klochkov
____________________ Racket Users list: http://lists.racket-lang.org/users
