From: Jim Pryor Date: Thu, 18 Nov 2010 18:12:03 +0000 (-0500) Subject: assignment7 tweaks X-Git-Url: http://lambda.jimpryor.net/git/gitweb.cgi?p=lambda.git;a=commitdiff_plain;h=2d5df0441175013c782ebee648a17043405ca251;ds=sidebyside assignment7 tweaks Signed-off-by: Jim Pryor --- diff --git a/hints/assignment_7_hint_2.mdwn b/hints/assignment_7_hint_2.mdwn index 9a208c78..d79f064c 100644 --- a/hints/assignment_7_hint_2.mdwn +++ b/hints/assignment_7_hint_2.mdwn @@ -1,5 +1,5 @@ -* GS&V's semantics involves elements from several different monads we've been looking at. First, they're working with (epistemic) modalities, so there are worlds playing a role like they did in [[Reader Monads for Intensionality]]. But we're going to ignore the modal element for this exercise. There's also variable binding, which is another reader monad. Next, there is a notion of a store, which some operations add new reference cells to. We implement this with a state monad (and so too do they, in effect, though they don't conceive of what they're doing in those terms). So we'll be working with a combination of both a reader monad for the variable binding and a state monad to keep track of the new "pegs" or reference cells. +* GS&V's semantics involves elements from several different monads we've been looking at. First, they're working with (epistemic) modalities, so there are worlds playing a role like they did in [[Reader Monad for Intensionality]]. But we're going to ignore the modal element for this exercise. There's also variable binding, which is another reader monad. Next, there is a notion of a store, which some operations add new reference cells to. We implement this with a state monad (and so too do they, in effect, though they don't conceive of what they're doing in those terms). So we'll be working with a combination of both a reader monad for the variable binding and a state monad to keep track of the new "pegs" or reference cells. There are systematic ways to layer different monads together. If you want to read about these, a keyword is "monad transformers." Ken Shan discusses them in [his paper](http://arxiv.org/abs/cs/0205026v1) that we recommended earlier.