From 3b34c82b4285eb9292c13c7fc3307df1056c05fa Mon Sep 17 00:00:00 2001
From: Richard Feldman <richard.t.feldman@gmail.com>
Date: Wed, 22 May 2019 21:54:55 -0400
Subject: [PATCH] Introduce Closure

---
 src/expr.rs  |  1 +
 src/parse.rs | 12 ++++++++++++
 2 files changed, 13 insertions(+)

diff --git a/src/expr.rs b/src/expr.rs
index e35019d3d5..f55803e038 100644
--- a/src/expr.rs
+++ b/src/expr.rs
@@ -15,6 +15,7 @@ pub enum Expr {
     Func(String, Box<Expr>),
     Apply(Box<Expr>, Box<Expr>),
     Operator(Box<Expr>, Operator, Box<Expr>),
+    Closure(Vec<Pattern>, Box<Expr>),
 
     If(Box<Expr>, Box<Expr>, Box<Expr>),
 }
diff --git a/src/parse.rs b/src/parse.rs
index c338286fe6..f80f266cc3 100644
--- a/src/parse.rs
+++ b/src/parse.rs
@@ -263,6 +263,18 @@ where I: Stream<Item = char, Position = IndentablePosition>,
         )
 }
 
+pub fn closure<I>(min_indent: i32) -> impl Parser<Input = I, Output = Expr>
+where I: Stream<Item = char, Position = IndentablePosition>,
+    I::Error: ParseError<I::Item, I::Range, I::Position>
+{
+    // TODO patterns must be separated by commas!
+    between(char('|'), char('|'), many1::<Vec<_>, _>(pattern()))
+        .and(expr_body(min_indent))
+        .map(|(patterns, closure_body)| {
+            Expr::Closure(patterns, Box::new(closure_body))
+        })
+}
+
 pub fn pattern<I>() -> impl Parser<Input = I, Output = Pattern>
 where I: Stream<Item = char, Position = IndentablePosition>,
     I::Error: ParseError<I::Item, I::Range, I::Position>