From 5c00b978b0bc0c1eeb64682cba6aa338fea320bf Mon Sep 17 00:00:00 2001
From: NanoTech
Date: Sun, 11 Dec 2016 23:27:36 -0600
Subject: Start implementing error explanations

---
 src/errors/MissingHandler.txt | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)
 create mode 100644 src/errors/MissingHandler.txt

(limited to 'src/errors/MissingHandler.txt')

diff --git a/src/errors/MissingHandler.txt b/src/errors/MissingHandler.txt
new file mode 100644
index 0000000..433445e
--- /dev/null
+++ b/src/errors/MissingHandler.txt
@@ -0,0 +1,32 @@
+Explanation: You can ❰merge❱ the alternatives of a union using a record with one
+handler per alternative, like this:
+
+
+    ┌─────────────────────────────────────────────────────────────────────┐
+    │     let union    = < Left = +2 | Right : Bool >                     │
+    │ in  let handlers = { Left = Natural/even, Right = λ(x : Bool) → x } │
+    │ in  merge handlers union : Bool                                     │
+    └─────────────────────────────────────────────────────────────────────┘
+
+
+... but you must provide exactly one handler per alternative in the union.  You
+cannot omit any handlers
+
+For example, the following expression is $_NOT valid:
+
+
+                                              Invalid: Missing ❰Right❱ handler
+                                              ⇩
+    ┌─────────────────────────────────────────────────┐
+    │     let handlers = { Left = Natural/even }      │
+    │ in  let union    = < Left = +2 | Right : Bool > │
+    │ in  merge handlers union : Bool                 │
+    └─────────────────────────────────────────────────┘
+
+
+Note that you need to provide handlers for other alternatives even if those
+alternatives are never used
+
+You need to supply the following handlers:
+
+↳ $txt0
-- 
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