From bbd73d5f4a02bd81cb185b20ff3722210b2c05f1 Mon Sep 17 00:00:00 2001
From: Michael Zhang <failed.down@gmail.com>
Date: Tue, 13 Feb 2018 17:43:40 -0600
Subject: [PATCH] initial

---
 .gitignore |  6 ++++++
 Makefile   | 28 ++++++++++++++++++++++++++++
 lambda.ml  | 26 ++++++++++++++++++++++++++
 lexer.mll  | 12 ++++++++++++
 parser.mly | 25 +++++++++++++++++++++++++
 types.ml   |  9 +++++++++
 6 files changed, 106 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 Makefile
 create mode 100644 lambda.ml
 create mode 100644 lexer.mll
 create mode 100644 parser.mly
 create mode 100644 types.ml

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..365e168
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,6 @@
+lexer.ml
+parser.ml
+parser.mli
+*.cmo
+*.cmi
+
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..0e2a1cd
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,28 @@
+.PHONY: all clean
+
+types.cmo: types.ml
+	ocamlc -o $@ -c $^
+
+parser: parser.mly
+	ocamlyacc $^
+
+parser.cmo: parser	
+	ocamlc -c parser.mli
+	ocamlc -c parser.ml
+
+lexer.cmo: lexer.ml
+	ocamlc -o $@ -c $^
+
+lexer.ml: parser.cmo
+	ocamllex lexer.mll
+
+lambda.cmo: lambda.ml
+	ocamlc -o $@ -c $^
+
+clean:
+	rm -f lexer.ml parser.ml parser.mli
+	rm -f *.cmo *.cmi
+
+all: types.cmo lexer.cmo parser.cmo lambda.cmo
+	ocaml types.cmo parser.cmo lexer.cmo lambda.cmo
+
diff --git a/lambda.ml b/lambda.ml
new file mode 100644
index 0000000..e2870d9
--- /dev/null
+++ b/lambda.ml
@@ -0,0 +1,26 @@
+open Lexer
+open Lexing
+open Parser
+open Types
+
+let rec string_of_term (t:term) =
+  match t with
+  | TmAbs(x, t1) ->
+      "(\\" ^ (String.make 1 x) ^ "." ^ (string_of_term t1) ^ ")"
+  | TmApp(t1, t2) ->
+      "(" ^ (string_of_term t1) ^ (string_of_term t2) ^ ")"
+  | TmVar(x) ->
+      String.make 1 x
+
+let _ =
+  try
+    let rec loop ctx =
+      print_string "> "; flush stdout;
+      let lexbuf = Lexing.from_channel stdin in
+      let result = Parser.main Lexer.token lexbuf in
+        print_endline (string_of_term result); flush stdout;
+        loop ctx in
+    loop []
+  with Lexer.Eof ->
+    print_endline "error";
+    exit 0
diff --git a/lexer.mll b/lexer.mll
new file mode 100644
index 0000000..f6ac937
--- /dev/null
+++ b/lexer.mll
@@ -0,0 +1,12 @@
+{
+  open Parser
+  exception Eof
+}
+
+rule token = parse
+  | ' ' | '\t' { token lexbuf }
+  | '\n' { EOL }
+  | '\\' { Lambda }
+  | '.' { Dot }
+  | ['a'-'z'] as c | ['A'-'Z'] as c { Ident(c) }
+  | eof { raise Eof }
diff --git a/parser.mly b/parser.mly
new file mode 100644
index 0000000..c2959bd
--- /dev/null
+++ b/parser.mly
@@ -0,0 +1,25 @@
+%{
+  open Types
+%}
+
+%token EOL
+%token Dot
+%token <char> Ident
+%token Lambda
+
+%start main
+%type <Types.term> main
+%%
+
+main:
+  expr EOL { $1 }
+;
+expr:
+  | var { Types.TmVar($1) }
+  | Lambda var Dot expr { Types.TmAbs($2, $4) }
+  | expr expr { Types.TmApp ($1, $2) }
+;
+var:
+  Ident { $1 }
+;
+
diff --git a/types.ml b/types.ml
new file mode 100644
index 0000000..83286fa
--- /dev/null
+++ b/types.ml
@@ -0,0 +1,9 @@
+type term =
+  | TmVar of char
+  | TmAbs of char * term
+  | TmApp of term * term
+
+type binding = NameBind
+
+type context = (char * binding) list
+