sample-code: Add demo for get_line()

sample-code/letter_frequency.cl

@@ -0,0 +1,44 @@
+#!/usr/bin/env -S conlang -r false
+// Showcases `get_line` behavior by sorting stdin
+
+fn in_range(this: Ord, min: Ord, max: Ord) -> bool {
+    min < this && this < max
+}
+
+fn frequency(s: str) -> [i32; 128] {
+    let letters = [0;128];
+    for letter in s {
+        if (letter).in_range(' ', letters.len() as char) {
+            letters[(letter as i32)] += 1;
+        }
+    }
+    letters
+}
+
+fn plot_freq(freq: [i32; 128]) -> str {
+    let buf = "";
+    for idx in 0..len(freq) {
+        for n in 0..(freq[idx]) {
+            buf += idx as char;
+        }
+    }
+    buf
+}
+
+const msg: str ="letter_frequency.cl
+Computes the frequency of ascii characters in a block of text, and prints it bucket-sorted.
+Press Ctrl+D to quit.";
+
+fn main () {
+    println(msg)
+    let lines = "";
+    loop {
+        let line = get_line();
+        if line == "" { break() }
+        lines += line;
+    }
+
+    let freq = frequency(lines)
+    let plot = plot_freq(freq)
+    println(plot)
+}