From ee5dd7b9123a9239e7646452773abe46fe272d30 Mon Sep 17 00:00:00 2001
From: Kjetil Orbekk <kjetil.orbekk@gmail.com>
Date: Sun, 27 Aug 2017 14:03:01 -0400
Subject: Add: 'some' tool reads random lines from input

---
 src/main.rs | 62 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 62 insertions(+)
 create mode 100644 src/main.rs

(limited to 'src')

diff --git a/src/main.rs b/src/main.rs
new file mode 100644
index 0000000..eda1c01
--- /dev/null
+++ b/src/main.rs
@@ -0,0 +1,62 @@
+extern crate clap;
+extern crate rand;
+
+use clap::{Arg, App};
+use std::collections::vec_deque::VecDeque;
+use std::io::{self, BufRead};
+use std::result::Result;
+
+fn some<R: rand::Rng, T: Iterator<Item = Result<String, io::Error>>>(
+    r: &mut R,
+    n: usize,
+    lines: T,
+) -> Result<VecDeque<String>, io::Error> {
+    let mut result: VecDeque<String> = VecDeque::with_capacity(n);
+    fn push(v: &mut VecDeque<String>, n: usize, x: String) {
+        v.push_back(x);
+        if v.len() > n {
+            v.pop_front();
+        }
+    };
+
+    for (i, line) in lines.enumerate() {
+        let line = line?;
+        if result.len() < n {
+            push(&mut result, n, line);
+        } else if r.gen_range(0, i) < n {
+            let victim = r.gen_range(0, n);
+            result.remove(victim);
+            push(&mut result, n, line);
+        }
+    }
+    return Ok(result);
+}
+
+fn main() {
+    let matches = App::new("some")
+        .version("0.1")
+        .author("Kjetil Ørbekk <kj@orbekk.com>")
+        .arg(
+            Arg::with_name("lines")
+                .short("n")
+                .value_name("NUM")
+                .help("Number of lines to print")
+                .takes_value(true),
+        )
+        .get_matches();
+    let num_lines = matches
+        .value_of("lines")
+        .unwrap_or("10")
+        .parse::<usize>()
+        .expect("number of lines to print");
+    let stdin = io::stdin();
+    let lines = some(&mut rand::thread_rng(), num_lines, stdin.lock().lines());
+    match lines {
+        Ok(lines) => {
+            for line in lines {
+                println!("{}", line);
+            }
+        }
+        Err(e) => println!("Error: {}", e),
+    }
+}
-- 
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