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At Sun, 7 Nov 2004 18:48:13 -0800 (PST), campbell@xxxxxxxxxxxxxxxxxxxxxxxxxxx wrote: > > On Tue, 28 Sep 2004, Alex Shinn wrote: > > > However, realistically most implementations either use a relative of > > TinyCLOS (for which slot-setting is customizable with the MOP and for > > immutable fields and left unchanged for mutable fields at no extra > > cost) or Meroon (which already supports immutable fields), so this > > isn't really an issue. > > This is a little late to add to the discussion, but I just want to > contest the claim that most serious Scheme systems that provide first- > class record type descriptors base/implement their record systems atop > CLOS-style frameworks such as Tiny-CLOS or Meroon. I can think of only > three implementations that do such a thing -- Gauche, RScheme, & STklos > --, whereas I can think of a very large number of others that either > don't support such frameworks at all or, if they do, don't base their > record systems on them (T, Scheme48, MIT Scheme, Gambit, Chicken, SISC, > Larceny, Chez, PLT, probably SCM & guile, and anything that uses SLIB > or Jonathan Rees's records proposal from the late '80s; there are also > surely a few more that elude my memory right now). So I don't think > it's really reasonable to just punt arguments on the basis that they're > solved automatically by such CLOS-style frameworks. Chicken's records *are* defined in terms of the native OO system which is Tiny-CLOS. Guile's records are likewise defined in terms of GOOPS (a Tiny-CLOS derivative). You're right that many of the others don't translate records directly into CLOS-style objects, but most of them do have a CLOS-style system and therefore could: http://groups.google.com/groups?hl=en&lr=&c2coff=1&selm=871xpwv30h.wl%40strelka.synthcode.com&rnum=2 The implementations that do not implement records in terms of an OO system generally implement them as something closer to a C struct. In C the record-type would not be a first-class object and you could implement immutability without a performance hit. Arguably if you do want first class types and introspection in Scheme (which could require runtime checks for immutability) then you are already moving away from the simple C structs and closer to a CLOS model. -- Alex