Initial data commit

Task/CRC-32/JavaScript/crc-32.js

@@ -0,0 +1,98 @@
+(() => {
+    'use strict';
+
+    // --------------------- CRC-32 ----------------------
+
+    // crc32 :: String -> Int
+    const crc32 = str => {
+        // table :: [Int]
+        const table = enumFromTo(0)(255).map(
+            n => take(9)(
+                iterate(
+                    x => (
+                        x & 1 ? (
+                            z => 0xEDB88320 ^ z
+                        ) : identity
+                    )(x >>> 1)
+                )(n)
+            )[8]
+        );
+        return chars(str).reduce(
+            (a, c) => (a >>> 8) ^ table[
+                (a ^ c.charCodeAt(0)) & 255
+            ],
+            -1
+        ) ^ -1;
+    };
+
+    // ---------------------- TEST -----------------------
+    // main :: IO ()
+    const main = () =>
+        showHex(
+            crc32('The quick brown fox jumps over the lazy dog')
+        );
+
+    // --------------------- GENERIC ---------------------
+
+    // chars :: String -> [Char]
+    const chars = s =>
+        s.split('');
+
+
+    // enumFromTo :: Int -> Int -> [Int]
+    const enumFromTo = m =>
+        n => !isNaN(m) ? (
+            Array.from({
+                length: 1 + n - m
+            }, (_, i) => m + i)
+        ) : enumFromTo_(m)(n);
+
+
+    // identity :: a -> a
+    const identity = x =>
+        // The identity function.
+        x;
+
+
+    // iterate :: (a -> a) -> a -> Gen [a]
+    const iterate = f =>
+        // An infinite list of repeated
+        // applications of f to x.
+        function* (x) {
+            let v = x;
+            while (true) {
+                yield(v);
+                v = f(v);
+            }
+        };
+
+
+    // showHex :: Int -> String
+    const showHex = n =>
+        // Hexadecimal string for a given integer.
+        '0x' + n.toString(16);
+
+
+    // take :: Int -> [a] -> [a]
+    // take :: Int -> String -> String
+    const take = n =>
+        // The first n elements of a list,
+        // string of characters, or stream.
+        xs => 'GeneratorFunction' !== xs
+        .constructor.constructor.name ? (
+            xs.slice(0, n)
+        ) : [].concat.apply([], Array.from({
+            length: n
+        }, () => {
+            const x = xs.next();
+            return x.done ? [] : [x.value];
+        }));
+
+
+    // MAIN -------------
+    const result = main();
+    return (
+        console.log(result),
+        result
+    );
+})();