Oops, I have to reply to myself. Matthew correctly reminded me that it is
call-by-value/pass-by-worth what I mean for Racket and Java not .../pass-by-reference. Sorry for the confusion. On Jul 20, 2014, at 6:27 PM, Matthias Felleisen <matth...@ccs.neu.edu> wrote: > > call-by is a notion of time, pass-by refers to entity that is used (location > if you so will). You can create a 2-dimension table of these options and > you'll be able to find some language for almost any cell in this table. > > The common meaning of call-by-value is call-by-value/pass-by-reference. Both > Java and Racket and a whole lot of languages use this combination. > Call-by-name is also a common reference to call-by-name/pass-by-reference, > see Algol 60 for an example. > > You can also create a calculus for any cell in this table. Google for Crank > and Felleisen and POPL and you'll find something. With that I mean > > (1) a calculus whose basic axiom(s) capture/s the mechanics of parameter > passing > (2) and that satisfies Church-Rosser and has a Standardization Theorem (which > defines a deterministic strategy for evaluation terms) > (3) and whose ST coincides with the conventional evaluator/abstract machine > > This holds for call-by-name, call-by-value (common meanings), in purely > functional or imperative settings, and it extends to call-by-copy and several > other mechanisms. > > The phrase "call-by-value is a reduction strategy" has no meaning per se but > is a left over from the time when people hadn't figured out the above (pre > 1070). > > It sounds like you're taking a course on PL and got some exercises to solve. > I am glad we can help, and I assume you will give credit to the mailing list. > > > > On Jul 20, 2014, at 2:44 PM, Jon Zeppieri wrote: > >> On Sun, Jul 20, 2014 at 5:02 AM, קוראל אלימלך <coral2...@gmail.com> wrote: >>> Hey :) >>> How the arguments are passed in racket? >>> by value/ reference/name? >>> >>> If u can add an example it will b good :) >>> Thank U ! >>> >> >> I suspect two different things are being conflated here: >> >> 1. the reduction semantics of the language >> 2. the question of whether or not data is copied at procedure-call >> boundaries. >> >> >> For (1), Racket's reduction strategy is call-by-value. As Jos Koot has >> demonstrated, in a procedure-call expression: >> >> (fn-expr argn-expr...) >> >> all of the sub-expressions will be reduced (that is, evaluated) to >> values before the function is applied. >> >> For (2), Racket does not copy data at procedure-call boundaries. If >> you pass a mutable struct, the callee is able to make changes to it >> that are visible to the caller. This is unlike in C, where you would >> need to pass a pointer to a struct in order to allow the callee to >> operate on the same instance as the caller. >> >> Unfortunately, "call-by-X" terminology is used to refer to both things >> and usually in ways that make matters far more confusing than they >> need be. See, e.g., >> [http://en.wikipedia.org/wiki/Evaluation_strategy], which is just >> awful. >> >> -Jon >> >> ____________________ >> Racket Users list: >> http://lists.racket-lang.org/users > ____________________ Racket Users list: http://lists.racket-lang.org/users
