Second rewrite attempt, this one should work, monkaS

1 files changed, 27 insertions, 0 deletions

diff --git a/src/__OLD_parcom/recover.cr b/src/__OLD_parcom/recover.cr
new file mode 100644
index 0000000..378f8d6
--- /dev/null
+++ b/src/__OLD_parcom/recover.cr
@@ -0,0 +1,27 @@
+require "./parser.cr"
+require "./optional.cr"
+require "./map.cr"
+
+module Parcom
+  # `Recover` is a `Parser` that tries to parse with another parser,
+  # but does not fail the parser chain if the wrapped parser fails.
+  # If the wrapped parser fails, a `Recover` will not modify the input
+  # stream, and return an arbitrary value of type `V` instead.
+  class Recover(T, V) < Parser(T, V)
+    @p : Map(T, V?, V)
+
+    # Accepts the parser to use, and the default value
+    # to return if the parser fails.
+    def initialize(p : Parser(T, V), default : V)
+      @p = Optional.new(p).map { |x| x.nil? ? default : x }
+    end
+
+    # Tries to parse with the given parser, succeeds with the
+    # default value instead of failing. This parser does not
+    # consume input if the wrapped parser fails.
+    def parse(tokens : Tokens(T)) : Result(T, V)
+      @p.parse(tokens)
+    end
+  end
+end
+