[wip] client generates applications with more than 2 terms

3 files changed, 74 insertions, 1 deletions

diff --git a/rust/src/ast.rs b/rust/src/ast.rs
index e70f323..29d548f 100644
--- a/rust/src/ast.rs
+++ b/rust/src/ast.rs
@@ -22,7 +22,13 @@ impl Display for Value {
             Value::Num(i) => write!(f, "{}", i),
             Value::Bool(b) => write!(f, "{}", b),
             Value::Sym(s) => write!(f, "{}", s),
-            Value::App(l, r) => write!(f, "({} {})", l, r),
+            Value::App(l, r) => {
+                if let App(l1, l2) = *l.clone() {
+                    write!(f, "({} {} {})", l1, l2, r)
+                } else {
+                    write!(f, "({} {})", l, r)
+                }
+            }
             Value::Lam(var, body) => write!(f, "(lam {} {})", var, body),
             Value::Def(var, value) => write!(f, "(def {} {})", var, value),
             Value::Let(var, value, body) => write!(f, "(let ({} {}) {})", var, value, body),
@@ -71,3 +77,32 @@ impl Arbitrary for Value {
         .boxed()
     }
 }
+
+#[cfg(test)]
+mod ast_tests {
+
+    use super::{
+        identifier,
+        Value::{self, *},
+    };
+    use proptest::collection::vec;
+    use proptest::prelude::*;
+
+    fn any_sym() -> impl Strategy<Value = Value> {
+        identifier().prop_map(Sym)
+    }
+
+    proptest! {
+
+       #[test]
+        fn display_multiple_applications_as_a_sequence(atoms in vec("[a-z]".prop_map(Sym), 2..10)) {
+            let init  = atoms.first().unwrap().clone();
+            let value = atoms.iter().skip(1).fold(init, |acc, expr| {
+              Value::App(Box::new(acc.clone()), Box::new(expr.clone()))
+            });
+            assert_eq!(value.to_string(),
+                       format!("({})",
+                               atoms.iter().map(|v| v.to_string()).collect::<Vec<String>>().join(" ")));
+      }
+    }
+}
diff --git a/rust/src/lambda.rs b/rust/src/lambda.rs
index e6102d8..ee5cb1f 100644
--- a/rust/src/lambda.rs
+++ b/rust/src/lambda.rs
@@ -115,6 +115,8 @@ pub fn generate_expr(size: u32, runner: &mut TestRunner) -> Value {
         4 => simple_app().new_tree(runner).unwrap().current(),
         5 => nested_simple_app().new_tree(runner).unwrap().current(),
         6 => simple_lambda().new_tree(runner).unwrap().current(),
+        7 => app_to_lambda().new_tree(runner).unwrap().current(),
+        8 => multi_app().new_tree(runner).unwrap().current(),
         _ => todo!(),
     }
 }
@@ -124,6 +126,11 @@ fn simple_app() -> impl Strategy<Value = Value> {
     (leaf.clone(), leaf.clone()).prop_map(|(l, r)| Value::App(Box::new(l), Box::new(r)))
 }
 
+fn multi_app() -> impl Strategy<Value = Value> {
+    let leaf = prop_oneof![any_num(), any_sym()];
+    (leaf.clone(), leaf.clone()).prop_map(|(l, r)| Value::App(Box::new(l), Box::new(r)))
+}
+
 fn any_num() -> impl Strategy<Value = Value> {
     any::<i32>().prop_map(Value::Num)
 }
@@ -140,9 +147,16 @@ fn any_sym() -> impl Strategy<Value = Value> {
 }
 
 fn simple_lambda() -> impl Strategy<Value = Value> {
+    // TODO: there's nothing to guarantee the variable appears in the body
     (ascii_identifier(), nested_simple_app()).prop_map(|(v, b)| Value::Lam(v, Box::new(b)))
 }
 
+fn app_to_lambda() -> impl Strategy<Value = Value> {
+    let lam = simple_lambda();
+    let arg = prop_oneof![any_num(), any_sym(), nested_simple_app()];
+    (lam, arg).prop_map(|(l, a)| Value::App(Box::new(l), Box::new(a)))
+}
+
 #[cfg(test)]
 mod lambda_test {
     use crate::parser::parse;
diff --git a/rust/src/web.rs b/rust/src/web.rs
index de87ad6..8fa9452 100644
--- a/rust/src/web.rs
+++ b/rust/src/web.rs
@@ -465,6 +465,30 @@ mod app_tests {
     }
 
     #[test]
+    async fn client_generates_application_with_lambda_terms_at_level_7() {
+        let mut client = client();
+        client.grade = 7;
+
+        let (input, _) = client.generate_expr();
+
+        let parsed = parse(&input);
+        match &parsed[..] {
+            [Value::App(t1, _)] if matches!(**t1, Value::Lam(_, _)) => (),
+            _ => panic!("Expected symbol, got {:?}", parsed),
+        }
+    }
+
+    #[test]
+    async fn client_generates_applications_with_more_than_2_terms_at_level_8() {
+        let mut client = client();
+        client.grade = 8;
+
+        let (input, _) = client.generate_expr();
+
+        assert!(input.split(' ').count() > 2);
+    }
+
+    #[test]
     async fn client_increases_grade_on_successful_test() {
         let mut client = client();
         let expected = "1".to_string();