From 62fa7ccd41bc7ea47783b23bb5ed0d6d60fcec5d Mon Sep 17 00:00:00 2001
From: mehbark <terezi@pyrope.net>
Date: Thu, 16 Apr 2026 12:58:31 -0400
Subject: [PATCH] avoid creating intermediate hashmap

---
 src/main.rs | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/src/main.rs b/src/main.rs
index 1a2fe33..5c68322 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -10,12 +10,12 @@ fn main() {
 
     for n in 1..=20 {
         let freqs = ngram_freqs(n, &src);
-        let bits = entropy(freqs.values().copied());
+        let bits = entropy(freqs);
         println!("{n:2}: {bits:6.3} bits, {:.3} bits/letter", bits / n as f64);
     }
 }
 
-fn ngram_freqs(n: usize, src: &[u8]) -> HashMap<Box<[u8]>, f64> {
+fn ngram_freqs(n: usize, src: &[u8]) -> impl Iterator<Item = f64> {
     assert!(n > 0);
 
     let mut counts: HashMap<Box<[u8]>, u64> = HashMap::new();
@@ -27,9 +27,8 @@ fn ngram_freqs(n: usize, src: &[u8]) -> HashMap<Box<[u8]>, f64> {
     let total_count: u64 = counts.values().sum();
 
     counts
-        .into_iter()
-        .map(|(k, v)| (k, v as f64 / total_count as f64))
-        .collect()
+        .into_values()
+        .map(move |p| p as f64 / total_count as f64)
 }
 
 fn entropy(probs: impl Iterator<Item = f64>) -> f64 {