From b274828831fec26cd8b3089ffef14cb96ce2de2f Mon Sep 17 00:00:00 2001
From: Matthew Hall <hallmatthew314@gmail.com>
Date: Thu, 16 Mar 2023 20:36:03 +1300
Subject: Second rewrite attempt, this one should work, monkaS

---
 src/__OLD_parcom/sep_by.cr | 38 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)
 create mode 100644 src/__OLD_parcom/sep_by.cr

(limited to 'src/__OLD_parcom/sep_by.cr')

diff --git a/src/__OLD_parcom/sep_by.cr b/src/__OLD_parcom/sep_by.cr
new file mode 100644
index 0000000..fa19027
--- /dev/null
+++ b/src/__OLD_parcom/sep_by.cr
@@ -0,0 +1,38 @@
+require "./parser.cr"
+require "./map.cr"
+require "./many.cr"
+
+module Parcom
+  # `SepBy` is a `Parser` that tries to parse one or more times with one
+  # parser, alternating with a second parser.
+  #
+  # Example:
+  # ```
+  # letter_a = Token.new('a')
+  # letter_b = Token.new('b')
+  # p = SepBy(Char, Car, Char).new(letter_a, letter_b)
+  # tokens = Tokens.from_string("ababababa")
+  #
+  # result = p.parse(tokens)
+  # puts result.value # => ['a', 'a', 'a', 'a', 'a']
+  # ```
+  class SepBy(T, V, U) < Parser(T, Array(V))
+    @p : Map(T, {V, Array(V)}, Array(V))
+
+    # Accepts the parser that parses the result values, and the
+    # parser that parses the sepatators.
+    def initialize(elem : Parser(T, V), sep : Parser(T, U))
+      @p = (elem + Many(T, U).new(sep >> elem)).map do |tup|
+        [tup[0]] + tup[1]
+      end
+    end
+
+    # Tries to parse, alternating the first and second parsers.
+    def parse(tokens : Tokens(T)) : Result(T, Array(V))
+      @p.parse(tokens)
+    rescue ex : ParserFail
+      raise ParserFail.new("SepBy: #{ex.message}")
+    end
+  end
+end
+
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