From 5b9e9849e8d2ccc54d798d2c4c65d58736262e12 Mon Sep 17 00:00:00 2001
From: PaddiM8 <paddim8@pm.me>
Date: Sat, 6 Jun 2020 14:55:30 +0200
Subject: [PATCH] Improved output.

---
 kalk_cli/src/output.rs | 46 +++++++++++++++++++++++++-----------------
 1 file changed, 27 insertions(+), 19 deletions(-)

diff --git a/kalk_cli/src/output.rs b/kalk_cli/src/output.rs
index d080061..3787e73 100644
--- a/kalk_cli/src/output.rs
+++ b/kalk_cli/src/output.rs
@@ -4,28 +4,36 @@ use kalk::parser::{self};
 pub fn eval(parser: &mut parser::Context, input: &str) {
     match parser::parse(parser, input, 53) {
         Ok(Some(result)) => {
+            let (_, digits, exp_option) = result.to_sign_string_exp(10, None);
+            let exp = if let Some(exp) = exp_option { exp } else { 0 };
+
             if result.is_infinite() {
                 err("Too big to process.");
-            } else if result > 100_000_000 || result < -100_000_00 {
-                let sign = if result >= 0 { "" } else { "-" };
-                let (_, digits, exp) = result.to_sign_string_exp(10, None);
-                let value = format!(
-                    "{}.{}",
-                    digits[0..1].to_string(),
-                    digits[1..].to_string().trim_end_matches('0')
-                );
-
-                println!("{}{}*10^{}", sign, value, exp.unwrap() - 1);
-            } else if result.clone().fract() == 0 {
-                println!("{}", result.to_integer().unwrap());
+            /*} else if result.clone().fract() == 0 {
+            println!("{}", result.to_integer().unwrap());*/
             } else {
-                println!(
-                    "{}",
-                    result
-                        .to_string()
-                        .trim_end_matches('0')
-                        .trim_end_matches('.')
-                );
+                let use_sci_notation = exp > 8 || exp < -6;
+                let comma_pos = if use_sci_notation { 1 } else { exp as usize };
+                let sign = if result >= 0 { "" } else { "-" };
+
+                let num = if use_sci_notation {
+                    // Insert the comma if there are supposed to be decimals.
+                    let mut chars: Vec<char> = digits.trim_end_matches('0').chars().collect();
+                    chars.insert(comma_pos, '.');
+                    chars.into_iter().collect::<String>()
+                } else if exp < 0 {
+                    // 0 < x < 1
+                    format!("0.{}{}", "0".repeat(exp.abs() as usize), digits)
+                } else {
+                    // Regular number
+                    digits[..(exp as usize)].to_string()
+                };
+
+                if use_sci_notation {
+                    println!("{}{}*10^{}", sign, num, exp);
+                } else {
+                    println!("{}{}", sign, num);
+                }
             }
         }
         Ok(None) => print!(""),