From 4f1181c51ee71bd229b7815fed80ac9a564611d2 Mon Sep 17 00:00:00 2001
From: Rob Rix <rob.rix@github.com>
Date: Fri, 18 Sep 2015 15:42:53 -0400
Subject: [PATCH] Add a delay combinator.

---
 prototype/Doubt/Parse.swift | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/prototype/Doubt/Parse.swift b/prototype/Doubt/Parse.swift
index d4a6bb1fa..c7c28a9ff 100644
--- a/prototype/Doubt/Parse.swift
+++ b/prototype/Doubt/Parse.swift
@@ -40,6 +40,12 @@ public func not<T>(parser: String -> State<T>?)(_ input: String) -> State<String
 }
 
 
+/// Delays evaluation of a parser.
+public func delay<A>(thunk: () -> String -> State<A>?) -> String -> State<A>? {
+	return { thunk()($0) }
+}
+
+
 public func parseWhile(predicate: Character -> Bool)(_ input: String) -> State<String>? {
 	return input.characters.count > 0 && predicate(input.characters[input.startIndex])
 		? parseWhile(predicate)(input.from(1)).map { State(rest: $0.rest, value: input.to(1) + $0.value) } ?? State(rest: input.from(1), value: input.to(1))