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-rw-r--r--demo/prose8
-rw-r--r--src/elaborate.sml17
2 files changed, 13 insertions, 12 deletions
diff --git a/demo/prose b/demo/prose
index 9c2639ff..a06b1ce5 100644
--- a/demo/prose
+++ b/demo/prose
@@ -197,3 +197,11 @@ react.urp
<p>Most client-side JavaScript programs modify page contents imperatively, but Ur/Web is based on functional-reactive programming instead. Programs allocate data sources and then describe the page as a pure function of those data sources. When the sources change, the page changes automatically.</p>
<p>Here's an example where a button modifies a data source that affects some text on the page. The affected portion of the page is indicated with the pseudo-HTML tag <tt>dyn</tt>, whose <tt>signal</tt> attribute specifies one of these pure functions over mutable sources. A source containing data of type <tt>t</tt> has type <tt>source t</tt> and is created with the <tt>source</tt> operation within the <tt>transaction</tt> monad. Functions over sources are represented in the monad <tt>signal</tt>. Like in Haskell, we overload monad notations, so that the same return and bind operators can be used to write signals and transactions. The <tt>signal</tt> function coerces a source to a signal.</p>
+
+listEdit.urp
+
+<p>This is a more involved functional-reactive example, involving recursive data structures that contain sources. We build a list editor similar to the one from the <tt>ListShop</tt> example, but with all editing happening on the client side.</p>
+
+<p>The central data structure is the <tt>rlist</tt>, a list whose individual elements are sources, enabling fine-grained mutation. Every rlist is either nil or is a cons cell made up of a source for a string data element, another source to serve as a scratchpad for GUI-based edits to the data element, and a final source that stores the remainder of the list.</p>
+
+<p>The main program provides operations to append to a list and to edit the data stored at any cell of the list. Append is implemented by maintaining a source <tt>head</tt>, which points to the first list element; and a source <tt>tailP</tt>, which points to a <tt>source rlist</tt> where we should place the next appended node.</p>
diff --git a/src/elaborate.sml b/src/elaborate.sml
index 5e94d8e4..daa6e004 100644
--- a/src/elaborate.sml
+++ b/src/elaborate.sml
@@ -706,13 +706,6 @@
("#2", p_summary env {fields = fs2, unifs = #unifs s2, others = #others s2})]*)
val (unifs1, unifs2) = eatMatching (fn ((_, r1), (_, r2)) => r1 = r2) (#unifs s1, #unifs s2)
- fun eatMost unifs =
- case unifs of
- (_, r) :: (rest as _ :: _) => (r := SOME (L'.CRecord (k, []), loc);
- eatMost rest)
- | _ => unifs
- val unifs1 = eatMost unifs1
- val unifs2 = eatMost unifs2
val (others1, others2) = eatMatching (consEq env) (#others s1, #others s2)
(*val () = eprefaces "Summaries3" [("#1", p_summary env {fields = fs1, unifs = unifs1, others = others1}),
@@ -887,6 +880,11 @@
(L'.CError, _) => ()
| (_, L'.CError) => ()
+ | (L'.CRecord _, _) => isRecord ()
+ | (_, L'.CRecord _) => isRecord ()
+ | (L'.CConcat _, _) => isRecord ()
+ | (_, L'.CConcat _) => isRecord ()
+
| (L'.CUnif (_, k1, _, r1), L'.CUnif (_, k2, _, r2)) =>
if r1 = r2 then
()
@@ -1034,11 +1032,6 @@
| (L'.TKFun (x, c1), L'.TKFun (_, c2)) =>
unifyCons' (E.pushKRel env x) c1 c2
- | (L'.CRecord _, _) => isRecord ()
- | (_, L'.CRecord _) => isRecord ()
- | (L'.CConcat _, _) => isRecord ()
- | (_, L'.CConcat _) => isRecord ()
-
| _ => err CIncompatible
end