From 262642438a20da76edd958b31a33fb3b4cbfef4d Mon Sep 17 00:00:00 2001
From: Stephen Celis <stephen@stephencelis.com>
Date: Sun, 12 May 2019 16:58:23 -0400
Subject: [PATCH] 57

---
 .../Parsers.playground/Contents.swift         | 78 +++++++++++++++++++
 .../Parsers.playground/contents.xcplayground  |  4 +
 0057-what-is-a-parser-pt2/README.md           |  5 ++
 README.md                                     |  1 +
 4 files changed, 88 insertions(+)
 create mode 100644 0057-what-is-a-parser-pt2/Parsers.playground/Contents.swift
 create mode 100644 0057-what-is-a-parser-pt2/Parsers.playground/contents.xcplayground
 create mode 100644 0057-what-is-a-parser-pt2/README.md

diff --git a/0057-what-is-a-parser-pt2/Parsers.playground/Contents.swift b/0057-what-is-a-parser-pt2/Parsers.playground/Contents.swift
new file mode 100644
index 00000000..082ece43
--- /dev/null
+++ b/0057-what-is-a-parser-pt2/Parsers.playground/Contents.swift
@@ -0,0 +1,78 @@
+//typealias Parser<A> = (String) -> A
+
+struct Parser<A> {
+//  let run: (String) -> A?
+//  let run: (String) -> (match: A?, rest: String)
+//  let run: (inout String) -> A?
+  let run: (inout Substring) -> A?
+
+  func run(_ str: String) -> (match: A?, rest: Substring) {
+    var str = str[...]
+    let match = self.run(&str)
+    return (match, str)
+  }
+}
+
+let int = Parser<Int> { str in
+  let prefix = str.prefix(while: { $0.isNumber })
+  guard let int = Int(prefix) else { return nil }
+  str.removeFirst(prefix.count)
+  return int
+}
+
+
+//Substring
+
+
+int.run("42")
+int.run("42 Hello World")
+int.run("Hello World")
+
+
+// (A)       -> A
+// (inout A) -> Void
+
+enum Route {
+  case home
+  case profile
+  case episodes
+  case episode(id: Int)
+}
+
+let router = Parser<Route> { str in
+  fatalError()
+}
+
+//router.run("/") // .home
+//router.run("/episodes/42") // .episode(42)
+
+//switch router.run("/episodes/42") {
+//case .none:
+//case .some(.home):
+//case .some(.profile):
+//case .some(.episodes):
+//case let .some(.episode(id)):
+//}
+
+import Foundation
+
+enum EnumPropertyGenerator {
+  case help
+  case version
+  case invoke(urls: [URL], dryRun: Bool)
+}
+
+let cli = Parser<EnumPropertyGenerator> { str in
+  fatalError()
+}
+
+//cli.run("generate-enum-properties --version") // .version
+//cli.run("generate-enum-properties --help") // .help
+//cli.run("generate-enum-properties --dry-run /path/to/file.swift") // .invoke(["/path/to/file.swift"], dryRun: true)
+//
+//switch cli.run("generate-enum-properties --dry-run /path/to/file.swift") {
+//case .help:
+//case .version:
+//case .invoke:
+//case nil:
+//}
diff --git a/0057-what-is-a-parser-pt2/Parsers.playground/contents.xcplayground b/0057-what-is-a-parser-pt2/Parsers.playground/contents.xcplayground
new file mode 100644
index 00000000..63b6dd8d
--- /dev/null
+++ b/0057-what-is-a-parser-pt2/Parsers.playground/contents.xcplayground
@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='macos'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>
\ No newline at end of file
diff --git a/0057-what-is-a-parser-pt2/README.md b/0057-what-is-a-parser-pt2/README.md
new file mode 100644
index 00000000..b8271b45
--- /dev/null
+++ b/0057-what-is-a-parser-pt2/README.md
@@ -0,0 +1,5 @@
+## [Point-Free](https://www.pointfree.co)
+
+> #### This directory contains code from Point-Free Episode: [What Is a Parser?: Part 2](https://www.pointfree.co/episodes/ep57-what-is-a-parser-part-2)
+>
+> TODO
diff --git a/README.md b/README.md
index c39c9f9c..61a95746 100644
--- a/README.md
+++ b/README.md
@@ -59,3 +59,4 @@ This repository is the home of code written on episodes of
 1. [Advanced Swift Syntax Enum Properties](0054-advanced-swift-syntax-enum-properties)
 1. [Swift Syntax Command Line Tool](0055-swift-syntax-command-line-tool)
 1. [What Is a Parser?: Part 1](0056-what-is-a-parser-pt1)
+1. [What Is a Parser?: Part 2](0057-what-is-a-parser-pt2)