From b5de8cf14fc4a6dba69bbffe655831c4fb2c292a Mon Sep 17 00:00:00 2001
From: Andrew Johnson <andrewjohnson@Andrews-MacBook-Pro.local>
Date: Mon, 7 May 2018 22:39:52 -0600
Subject: [PATCH] work on explaining parser combinators

---
 Chapter07/Cargo.toml            |  1 +
 Chapter07/combinator_pattern.rs | 71 +++++++++++++++++++++++++++++++++
 2 files changed, 72 insertions(+)

diff --git a/Chapter07/Cargo.toml b/Chapter07/Cargo.toml
index a397d8e..a6efc01 100644
--- a/Chapter07/Cargo.toml
+++ b/Chapter07/Cargo.toml
@@ -3,6 +3,7 @@ name = "Chapter7"
 version = "1.0.0"
 
 [dependencies]
+chomp = "0.3.1"
 
 [[bin]]
 name = "functor_pattern"
diff --git a/Chapter07/combinator_pattern.rs b/Chapter07/combinator_pattern.rs
index 2a86f1d..66fc828 100644
--- a/Chapter07/combinator_pattern.rs
+++ b/Chapter07/combinator_pattern.rs
@@ -1,3 +1,69 @@
+#[macro_use]
+extern crate chomp;
+use chomp::prelude::*;
+
+#[derive(Debug, Eq, PartialEq)]
+struct Name<B: Buffer> {
+    first: B,
+    last:  B,
+}
+
+fn name<I: U8Input>(i: I) -> SimpleResult<I, Name<I::Buffer>> {
+    parse!{i;
+        let first = take_while1(|c| c != b' ');
+                    token(b' ');  // skipping this char
+        let last  = take_while1(|c| c != b'\n');
+
+        ret Name{
+            first: first,
+            last:  last,
+        }
+    }
+}
+
+
+trait ParseState<A> {
+   fn next(&self) -> (Box<ParseState<A>>,Option<char>);
+}
+struct ParseRCon<A,B>(A,Result<Option<B>,String>);
+enum ParseOutput<A> {
+   Success(A),
+   Failure(String)
+}
+
+fn parse_token<St,A,T>(t: T) -> impl (Fn(Box<ParseState<St>>) -> ParseRCon<Box<ParseState<St>>,A>)
+   where T: 'static + Fn(char) -> Option<A> {
+   move |st: Box<ParseState<St>>| {
+      let (next_state,next_char) = st.next();
+      match next_char {
+         Some(c) => ParseRCon(next_state,Ok(t(c))),
+         None => ParseRCon(st,Err("end of input".to_string()))
+      }
+   }
+}
+
+fn parse_satisfy<St,T>(t: T) -> impl (Fn(Box<ParseState<St>>) -> ParseRCon<Box<ParseState<St>>,char>)
+   where T: 'static + Fn(char) -> bool {
+   parse_token(move |c| if t(c) {Some(c)} else {None})
+}
+
+/*
+TODO
+  val return : 'a -> ('st, 'a) parser      
+  val (>>=)  : ('st, 'a) parser -> ('a -> ('st, 'b) parser) -> 
+               ('st, 'b) parser
+  val mzero  : ('st, 'a) parser
+  val mplus  : ('st, 'a) parser -> ('st, 'a) parser -> 
+               ('st, 'a) parser
+  val (>>)   : ('st, 'a) parser -> ('st, 'b) parser ->
+               ('st, 'b) parser
+
+  val chars  : char list -> ('st,char list) char_parser
+  many
+  sepBy
+  <|>
+*/
+
 fn compose<A,B,C,F,G>(f: F, g: G) -> impl Fn(A) -> C
    where F: 'static + Fn(A) -> B,
          G: 'static + Fn(B) -> C {
@@ -14,4 +80,9 @@ fn main()
    println!("g(1) = {}", g(1));
    println!("g(12) = {}", g(12));
    println!("g(123) = {}", g(123));
+
+   let parse_result = parse_only(name, "Martin Wernstål\n".as_bytes()).unwrap();
+   println!("first:{} last:{}",
+            String::from_utf8_lossy(parse_result.first),
+            String::from_utf8_lossy(parse_result.last));
 }