From a3ec0a57f85203742024316e255aede0b1f4f881 Mon Sep 17 00:00:00 2001
From: Laifsyn <99366187+Laifsyn@users.noreply.github.com>
Date: Wed, 5 Jun 2024 07:32:20 -0500
Subject: [PATCH] =?UTF-8?q?Usar=20Tailcall=20Implementar=20versi=C3=B3n=20?=
 =?UTF-8?q?con=20tailcall=20para=20evitar=20stackoverflow=20en=20entradas?=
 =?UTF-8?q?=20relativamente=20grandes?=
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---
 .../com/utp/clsEstructuraDatos/Cargo.toml     |  4 ++++
 .../laboratorio_2_rust/main.rs                | 21 ++++++++++++++++++-
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/src/main/java/com/utp/clsEstructuraDatos/Cargo.toml b/src/main/java/com/utp/clsEstructuraDatos/Cargo.toml
index c91bc9b..5803888 100644
--- a/src/main/java/com/utp/clsEstructuraDatos/Cargo.toml
+++ b/src/main/java/com/utp/clsEstructuraDatos/Cargo.toml
@@ -13,3 +13,7 @@ path = "laboratorio_2_rust/main.rs"
 colored = "2.1.0"
 inquire = "0.7.5"
 num-bigint = "0.4.5"
+tailcall = "1.0.1"
+
+[features]
+tailcall = []
diff --git a/src/main/java/com/utp/clsEstructuraDatos/laboratorio_2_rust/main.rs b/src/main/java/com/utp/clsEstructuraDatos/laboratorio_2_rust/main.rs
index 2eeba6f..46ae014 100644
--- a/src/main/java/com/utp/clsEstructuraDatos/laboratorio_2_rust/main.rs
+++ b/src/main/java/com/utp/clsEstructuraDatos/laboratorio_2_rust/main.rs
@@ -59,6 +59,7 @@ fn spawn_app() {
                 }
             };
         };
+        
         // Ejecutar la función seleccionada
         #[rustfmt::skip]
         match funcion {
@@ -76,7 +77,7 @@ fn spawn_app() {
                     println!("{}", format!("Factorial({}) no es calculable", args[0]).bright_red().bold());
                     continue;
                 };
-                println!("Factorial({}) = {factorial} ({} digitos)", args[0], factorial.to_string().len());
+                println!("Factorial({}) = {factorial} \n{}", args[0], format!("({} digitos)", factorial.to_string().len()).on_black().cyan());
             },            
         };
         match Confirm::new("Desea salir?").with_placeholder("Y/N").prompt() {
@@ -168,6 +169,7 @@ fn fib(nth: usize) -> Option<u128> {
 }
 
 /// Factorial Recursivo
+#[cfg(not(feature = "tailcall"))]
 fn factorial(n: usize) -> Option<num_bigint::BigInt> {
     if let 0..=1 = n {
         return Some(1.into());
@@ -176,6 +178,23 @@ fn factorial(n: usize) -> Option<num_bigint::BigInt> {
     }
 }
 
+/// Factorial Recursivo
+/// Compilar con `tailcall` para obtener esta función
+/// `cargo run --release --features "tailcall"`
+#[cfg(feature = "tailcall")]
+fn factorial<T:TryInto<u16>>(n: T) -> Option<num_bigint::BigUint> {
+    use num_bigint::BigUint;
+    let n = n.try_into().ok()?;
+    #[tailcall::tailcall]
+    fn tail_recursive_factorial(n: u16, acc: BigUint) -> BigUint {
+        match n {
+            0 => acc,
+            _ => tail_recursive_factorial(n - 1, acc * n)
+        }
+    }
+    return Some(tail_recursive_factorial(n, 1u8.into()));
+}
+
 fn Q(a: usize, b: usize) -> usize {
     if a < b {
         return 0;