From 7d7129222a3f15786ecebeb557eb4874304a6c7d Mon Sep 17 00:00:00 2001
From: Gavin Panella <gavin@gromper.net>
Date: Sat, 3 Nov 2018 16:00:38 +0100
Subject: [PATCH] Fix unicode escape decode bug in `DoubleQuoteString` example.

Previously \u Unicode escape codes of between 4 and 6 characters were being
rejected, whereas the error message indicates that the inverse should be the
behavior.

The example has also been extended to use all recognized escape sequences (\n,
\r, \t, \u) and give more information about what's happening.
---
 examples/DoubleQuoteString.elm | 22 +++++++++++++++++++---
 1 file changed, 19 insertions(+), 3 deletions(-)

diff --git a/examples/DoubleQuoteString.elm b/examples/DoubleQuoteString.elm
index 31ac621..0c26a59 100644
--- a/examples/DoubleQuoteString.elm
+++ b/examples/DoubleQuoteString.elm
@@ -9,9 +9,25 @@ import Parser exposing (..)
 
 
 main =
-  Html.text <| Debug.toString <|
-    run string "\"hello\""
+  let
+    input =
+      "\"Hell\\u{006f}! What's up?\\r\\nThis >\\t< is a tab, that's what.\\r\\n\\u{1f600}\""
+
+    result =
+      run string input
 
+    display text =
+      [ Html.dt [] [ Html.text "Rendered:" ]
+      , Html.dd [] [ Html.pre [] [ Html.text text ] ]
+      ]
+  in
+  Html.dl [] <|
+    [ Html.dt [] [ Html.text "Input:" ]
+    , Html.dd [] [ Html.pre [] [ Html.text input ] ]
+    , Html.dt [] [ Html.text "Parse result:" ]
+    , Html.dd [] [ Html.pre [] [ Html.text <| Debug.toString result ] ]
+    ]
+      ++ (Result.map display result |> Result.withDefault [])
 
 
 -- STRINGS
@@ -67,7 +83,7 @@ codeToChar str =
     length = String.length str
     code = String.foldl addHex 0 str
   in
-  if 4 <= length && length <= 6 then
+  if length < 4 || length > 6 then
     problem "code point must have between 4 and 6 digits"
   else if 0 <= code && code <= 0x10FFFF then
     succeed (Char.fromCode code)