feat: add ln function

this one is easier than log or root, because it only takes one arg

src/main.rs

@@ -7,14 +7,15 @@ use std::{
 use tylc as lib;
 
 fn main() -> ExitCode {
-    let input = match env::args().skip(1).rev().reduce(|x, a| a + &x) {
-        Some(s) => s,
-        None => {
+    let input = env::args()
+        .skip(1)
+        .rev()
+        .reduce(|x, a| a + &x)
+        .unwrap_or_else(|| {
             let mut buf = String::new();
             io::stdin().read_to_string(&mut buf).unwrap();
             buf
-        }
-    };
+        });
 
     match lib::formatting::pretty_eval(input, 10) {
         Ok(s) => println!("{s}"),

src/nodes/eval.rs

@@ -52,6 +52,8 @@ fn collapse_toplevel(nodes: &mut Vec<Node>, mut end: usize) -> Result<(), Error>
             Node::Number(n) => match variant {
                 Function::Sqrt => n.sqrt_mut(),
 
+                Function::Ln => n.ln_mut(),
+
                 Function::Sine => n.sin_mut(),
                 Function::ArcSine => n.asin_mut(),
                 Function::Cosine => n.cos_mut(),

src/nodes/mod.rs

@@ -76,6 +76,8 @@ pub enum Operator {
 pub enum Function {
     Sqrt,
 
+    Ln,
+
     Sine,
     ArcSine,
     Cosine,

src/nodes/parse.rs

@@ -37,6 +37,8 @@ impl FromStr for Function {
         match s {
             "sqrt" => Ok(Self::Sqrt),
 
+            "ln" => Ok(Self::Ln),
+
             "sin" => Ok(Self::Sine),
             "asin" => Ok(Self::ArcSine),
             "cos" => Ok(Self::Cosine),