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Per Bothner <per@xxxxxxxxxxx> writes:
> Ok, let's finalize it then. Thanks for your patience.
Ooops. Mikael Djurfeldt <mdj@xxxxxxxxxxxxxxx> just mailed me
a suggested formal syntax and semantics. I'm just about to go
to bed, so I haven't had a chance to more than glance it, but it
seems to make sense to edit it in. What do you people more
experienced in these things think?
I [i.e. Mikael] chose between an intuitive version which cuts pretty
deeply into the semantics of Scheme and a more conservative version
which was less intuitive. I chose the former because of its clarity.
Though, it's worth noting that the change is less deep than it looks
like: We basically only add a new applicable type, and most
implementations in practise already have several applicable types
(several types of procedures, continuations etc).
----------------------------------------------------------------------
Extensions to formal syntax:
1. <generalized assignment> is substituted for <assignment> in the
production for <expression>.
2. The following two productions are added:
<generalized assignment> --> (set! <access spec> <expression>)
<access spec> --> <variable>
| <procedure call>
----------------------------------------------------------------------
Extensions to formal semantics:
Abstract syntax:
1. A new alternative for `set!' is added to the production for Exp:
Exp --> K | ... | (set! (E0 E*) E1)
Domain equations:
2. The following equation is added:
Fs = L x (E* --> K --> C) x F
3. The equation for E is extended with Fs, i.e. it changes from
E = Q + H + R + Ep + Ev + Es + M + F
to
E = Q + H + R + Ep + Ev + Es + M + F + Fs
Semantic functions:
4. The following definition is added:
E[[ (set! (E0 E*) E1) ]] = E[[ ((setter E0) E* E1) ]]
Auxiliary functions:
5. `applicate' is changed from
lambda e e* k . e belongs to F --> (e | F ref 2) e* k,
wrong "bad procedure"
to
lambda e e* k . e belongs to F --> (e | F ref 2) e* k,
e belongs to Fs --> (e | Fs ref 2) e* k,
wrong "bad procedure"
6. The following functions are added:
setter: E* --> K --> C
setter = onearg(lambda e k . e belongs to Fs --> send(e | Fs ref 3 in E),
wrong "bad procedure with setter")
getter-with-setter: E* --> K --> C
getter-with-setter =
twoarg(lambda e1 e2 k sigma . e1 belongs to F -->
(e2 belongs to F -->
(new sigma belongs to L -->
send(<new sigma, e1 | F ref 2, e2 | F> in E)
k
(update (new sigma | L) unspecified sigma),
wrong "out of memory" sigma),
wrong "bad procedure in second argument"),
wrong "bad procedure in first argument")
--
--Per Bothner
per@xxxxxxxxxxx http://www.bothner.com/~per/