From 0c56405b4da55c8539b54f79cc4b720ad0243f0e Mon Sep 17 00:00:00 2001
From: Cassie Jones <code@witchoflight.com>
Date: Thu, 27 Feb 2020 14:19:40 +0100
Subject: [PATCH] An s-expression parser and an example program

This is intended to be a slightly fancier lambda calculus with
arithmetic support. The way I've written the example here suggests not
making conditionals a builtin, and instead just using church encodings.
This will probably be bad for displaying data purposes? I'm not sure how
I want to handle I/O. Maybe do an ML and put impure I/O in here?
---
 .gitignore  |  1 +
 Cargo.lock  | 14 ++++++++++++++
 Cargo.toml  | 10 ++++++++++
 README.md   |  3 +++
 program.vy  | 11 +++++++++++
 src/main.rs | 25 +++++++++++++++++++++++++
 6 files changed, 64 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 Cargo.lock
 create mode 100644 Cargo.toml
 create mode 100644 README.md
 create mode 100644 program.vy
 create mode 100644 src/main.rs

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..ea8c4bf
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+/target
diff --git a/Cargo.lock b/Cargo.lock
new file mode 100644
index 0000000..fb1b2ed
--- /dev/null
+++ b/Cargo.lock
@@ -0,0 +1,14 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+[[package]]
+name = "ess"
+version = "0.4.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c70ece3a2affa9eda5d916d778fe80fe2b7357aeb2d7b38f35286cfa983571d0"
+
+[[package]]
+name = "ivy"
+version = "0.1.0"
+dependencies = [
+ "ess",
+]
diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..e3a65aa
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,10 @@
+[package]
+name = "ivy"
+version = "0.1.0"
+authors = ["Cassie Jones <code@witchoflight.com>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+ess = "0.4.2"
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..97da433
--- /dev/null
+++ b/README.md
@@ -0,0 +1,3 @@
+# Ivy
+
+Little lambdas eat ivy.
diff --git a/program.vy b/program.vy
new file mode 100644
index 0000000..f226258
--- /dev/null
+++ b/program.vy
@@ -0,0 +1,11 @@
+(let ([nil (lam (c n) (n))]
+      [cons (lam (x y) (lam (c n) (c x y)))]
+      [fix (lam (f) (f f))]
+      [if (lam (c t f) ((c t f)))]
+      [true (lam (t f) t)]
+      [false (lam (t f) f)])
+    ([fix (lam (recur a b l n)
+        (if (<= n 0)
+            [lam () l]
+            [lam () (recur b (+ a b) (cons a l) (- n 1))]))]
+        0 1 nil 20))
diff --git a/src/main.rs b/src/main.rs
new file mode 100644
index 0000000..4f09f59
--- /dev/null
+++ b/src/main.rs
@@ -0,0 +1,25 @@
+use ess::{self, Sexp, parser::ParseError};
+use std::io::{self, Read};
+
+fn parse(input: &str) -> Result<Sexp, ParseError> {
+    let (sexp, rest) = ess::parse_one(input)?;
+    if !rest.trim().is_empty() {
+        return Err(ParseError::Unexpected('\0', sexp.get_loc().1));
+    }
+    Ok(sexp)
+}
+
+fn main() -> io::Result<()> {
+    let stdin = std::io::stdin();
+    let mut text = String::new();
+    stdin.lock().read_to_string(&mut text)?;
+    let item = match parse(&text) {
+        Ok(item) => item,
+        Err(err) => {
+            println!("{:?}", err);
+            std::process::exit(1);
+        }
+    };
+    println!("{:?}", item);
+    Ok(())
+}
-- 
2.43.2