From: Jim Pryor Date: Mon, 22 Nov 2010 10:50:57 +0000 (-0500) Subject: assign7 tweak X-Git-Url: http://lambda.jimpryor.net/git/gitweb.cgi?p=lambda.git;a=commitdiff_plain;h=7b80daef951f850ecab4e539d103607c7808d73b;hp=55a603b0e0ef6a5d020f3b025ec87b1bef17c7a7 assign7 tweak Signed-off-by: Jim Pryor --- diff --git a/assignment7.mdwn b/assignment7.mdwn index 5db178b2..d6cb6813 100644 --- a/assignment7.mdwn +++ b/assignment7.mdwn @@ -19,7 +19,7 @@ * You don't need to re-express the epistemic modality part of their semantics, just their treatment of extensional predicate logic. Though extra credit if you want to do the whole thing. - * You'll want to use the implementation of "implicitly represented" mutable variables that we discussed at the end of this week's meeting, or the "state monad" Chris presented, which is a simple version of the former. + * You'll want to use "implicitly represented" mutable variables, or a State monad. * Here are some [hints](/hints/assignment_7_hint_1). diff --git a/hints/assignment_7_hint_1.mdwn b/hints/assignment_7_hint_1.mdwn index ac15e19b..a68c826a 100644 --- a/hints/assignment_7_hint_1.mdwn +++ b/hints/assignment_7_hint_1.mdwn @@ -5,9 +5,9 @@ * Where they say "reference system," which they use the letter `r` for, that corresponds to what we've been calling "assignments", and have been using the letter `g` for. -* Where they say `r[x/n]`, that's our `g{x:=n}`, or in OCaml, `fun var -> if var = 'x' then n else g var`. +* Where they say `r[x/n]`, that's our `g{x:=n}`, which we could represent in OCaml as `fun var -> if var = 'x' then n else g var`. (Earlier we represented assignments as lists of pairs, here we're representing them as functions. Either can work.) -* Their function `g`, which assigns entities from the domain to pegs, corresponds to our store function, which assigns entities to indexes. To avoid confusion, I'll use `r` for assignments, like they do, and avoid using `g` altogether. Instead I'll use `h` for stores. (We can't use `s` because GS&V use that for something else, which they call "information states.") +* Their function `g`, which assigns entities from the domain to pegs, corresponds to a store with several indexes. To avoid confusion, I'll use `r` for assignments, like they do, and avoid using `g` altogether. Instead I'll use `h` for stores. (We can't use `s` because GS&V use that for something else, which they call "information states.") * At several places they talk about some things being *real extensions* of other things. This confused me at first, because they don't ever define a notion of "real extension." (They do define what they mean by "extensions.") Eventually, it emerges that what they mean is what I'd call a *proper extension*: an extension which isn't identical to the original.