From e5d9aee00b0c775df1d8e2d8819aeb80dffa73c2 Mon Sep 17 00:00:00 2001 From: Nadrieril Date: Fri, 1 Mar 2019 17:28:19 +0100 Subject: Split abnf_to_pest and dhall into their own crates --- dhall/src/errors/MissingHandler.txt | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+) create mode 100644 dhall/src/errors/MissingHandler.txt (limited to 'dhall/src/errors/MissingHandler.txt') diff --git a/dhall/src/errors/MissingHandler.txt b/dhall/src/errors/MissingHandler.txt new file mode 100644 index 0000000..433445e --- /dev/null +++ b/dhall/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 -- cgit v1.2.3