From b849745636c17a9015198c2a1865b8dbb43ff4a3 Mon Sep 17 00:00:00 2001
From: Arnaud Bailly <arnaud.bailly@iohk.io>
Date: Wed, 25 Sep 2024 12:12:53 +0200
Subject: Prepare parser to return multiple values

---
 rust/src/lambda.rs | 35 +++++++++++++++++++++--------------
 1 file changed, 21 insertions(+), 14 deletions(-)

(limited to 'rust/src/lambda.rs')

diff --git a/rust/src/lambda.rs b/rust/src/lambda.rs
index a6da87b..41c0c26 100644
--- a/rust/src/lambda.rs
+++ b/rust/src/lambda.rs
@@ -7,12 +7,15 @@ use ast::*;
 mod parser;
 use parser::*;
 
-pub fn run(arg: &str) -> String {
-    let content = read_to_string(arg).unwrap();
-    let value = parse(&content.to_string());
-    let result = eval(&value);
-
-    result.to_string()
+pub fn eval_file(file_name: &str) -> String {
+    let content = read_to_string(file_name).unwrap();
+    let values = parse(&content.to_string());
+    values
+        .iter()
+        .map(eval)
+        .map(|v| v.to_string())
+        .collect::<Vec<String>>()
+        .join(" ")
 }
 
 fn eval(arg: &Value) -> Value {
@@ -73,27 +76,31 @@ fn gensym() -> String {
 mod lambda_test {
     use crate::{eval, parse, Value};
 
+    fn parse1(string: &str) -> Value {
+        parse(string).pop().unwrap()
+    }
+
     #[test]
     fn evaluating_a_non_reducible_value_yields_itself() {
-        let value = parse("(foo 12)");
+        let value = parse1("(foo 12)");
         assert_eq!(value, eval(&value));
     }
 
     #[test]
     fn evaluating_application_on_an_abstraction_reduces_it() {
-        let value = parse("((lam x x) 12)");
+        let value = parse1("((lam x x) 12)");
         assert_eq!(Value::Num(12), eval(&value));
     }
 
     #[test]
     fn substitution_occurs_within_abstraction_body() {
-        let value = parse("(((lam x (lam y x)) 13) 12)");
+        let value = parse1("(((lam x (lam y x)) 13) 12)");
         assert_eq!(Value::Num(13), eval(&value));
     }
 
     #[test]
     fn substitution_occurs_within_application_body() {
-        let value = parse("(((lam x (lam y (y x))) 13) 12)");
+        let value = parse1("(((lam x (lam y (y x))) 13) 12)");
         assert_eq!(
             Value::App(Box::new(Value::Num(12)), Box::new(Value::Num(13))),
             eval(&value)
@@ -102,26 +109,26 @@ mod lambda_test {
 
     #[test]
     fn substitution_does_not_capture_free_variables() {
-        let value = parse("(((lam x (lam x x)) 13) 12)");
+        let value = parse1("(((lam x (lam x x)) 13) 12)");
         assert_eq!(Value::Num(12), eval(&value));
     }
 
     #[test]
     fn interpretation_applies_to_both_sides_of_application() {
-        let value = parse("((lam x x) ((lam x x) 12))");
+        let value = parse1("((lam x x) ((lam x x) 12))");
         assert_eq!(Value::Num(12), eval(&value));
     }
 
     #[test]
     fn reduction_is_applied_until_normal_form_is_reached() {
-        let value = parse("((((lam y (lam x (lam y (x y)))) 13) (lam x x)) 11)");
+        let value = parse1("((((lam y (lam x (lam y (x y)))) 13) (lam x x)) 11)");
         assert_eq!(Value::Num(11), eval(&value));
     }
 
     #[test]
     fn reduction_always_select_leftmost_outermost_redex() {
         // this should not terminate if we evaluate the rightmost redex first
-        let value = parse("((lam x 1) ((lam x (x x)) (lam x (x x))))");
+        let value = parse1("((lam x 1) ((lam x (x x)) (lam x (x x))))");
         assert_eq!(Value::Num(1), eval(&value));
     }
 }
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