Sorry, you might not like my answer, but I feel like the right next step
for you is to read (or reread) a tutorial about monadic programming in
Haskell. There's a pretty basic problem in your code below, and I feel
like it should be easy to avoid with an understanding of what monadic
code is, rather than just pattern-matching specific cases.
On 07/19/2015 06:49 PM, Stefan Scott Alexander wrote:
An excerpt from my code is shown below. In this scenario, the user is
editing a "child" record, using a data-bound <select> widget to select
a primary key in the "parent" table, called `status`:
Widget = (fn [nm :: Name] =>
let
val statusOptionsList =
queryL1 (SELECT Id, Nam FROM status ORDER BY Nam)
val statusOptions =
List.mapX
(fn r => <xml><option>{r.Nam}</option></xml>)
statusOptionsList (* <<== LINE 44 IN ERR MSG BELOW! *)
in
<xml>
<select{nm}>
{statusOptions}
</select>
</xml>
end)
I keep getting errors "unification failure" and "incompatible
constructors", eg:
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