From 3e970f7aa51c69d7e659392120722ebc1611b4d6 Mon Sep 17 00:00:00 2001
From: Matthew Hall <hallmatthew314@gmail.com>
Date: Thu, 9 Mar 2023 00:28:39 +1300
Subject: Rewrite Recover in terms of Optional

---
 src/parcom.cr | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/src/parcom.cr b/src/parcom.cr
index c1eb676..9e90562 100644
--- a/src/parcom.cr
+++ b/src/parcom.cr
@@ -67,10 +67,12 @@ module Parcom
       Plus.new(self, other)
     end
 
+    # TODO: allow/change to support block invocation
     def assert(f : V -> Bool)
       Assert.new(self, f)
     end
 
+    # TODO: allow/change to support block invocation
     def map(f : V -> U) : Map(T, V, U) forall U
       Map.new(self, f)
     end
@@ -116,6 +118,7 @@ module Parcom
     end
   end
 
+  # TODO: allow/change to support block invocation
   class Assert(T, V) < Parser(T, V)
     def initialize(@p : Parser(T, V), @f : V -> Bool)
     end
@@ -131,6 +134,7 @@ module Parcom
     end
   end
 
+  # TODO: allow/change to support block invocation
   class Satisfy(T) < Parser(T, T)
     def initialize(@f : T -> Bool)
     end
@@ -160,6 +164,7 @@ module Parcom
     end
   end
 
+  # TODO: allow/change to support block invocation
   class Map(T, V, U) < Parser(T, U)
     def initialize(@p : Parser(T, V), @f : V -> U)
     end
@@ -197,11 +202,15 @@ module Parcom
   end
 
   class Recover(T, V) < Parser(T, V)
-    def initialize(@p : Parser(T, V), @default : V)
+    @p : Map(T, V?, V)
+
+    def initialize(p : Parser(T, V), default : V)
+      f = ->(x : V?) { x.nil? ? default : x }
+      @p = Optional.new(p).map(f)
     end
 
     def parse(tokens : TokenStream(T)) : Result(T, V)
-      @p.parse?(tokens) || Result.new(tokens, @default)
+      @p.parse(tokens)
     end
   end
 
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