September Morn Update

Task/Semordnilap/JavaScript/semordnilap-3.js

@@ -0,0 +1,60 @@
+(() => {
+    'use strict';
+
+    // semordnilap :: [String] -> String
+    const semordnilap = xs => {
+        const go = ([s, ws], w) =>
+            s.has(w.split('').reverse().join('')) ? (
+                [s, [w].concat(ws)]
+            ) : [s.add(w), ws];
+        return xs.reduce(go, [new Set(), []])[1];
+    };
+
+    const main = () => {
+
+        // xs :: [String]
+        const xs = semordnilap(
+            lines(readFile('unixdict.txt'))
+        );
+
+        console.log(xs.length);
+        xs.filter(x => 4 < x.length).forEach(
+            x => showLog(...[x, x.split('').reverse().join('')])
+        )
+    };
+
+
+    // GENERIC FUNCTIONS ----------------------------
+
+    // lines :: String -> [String]
+    const lines = s => s.split(/[\r\n]/);
+
+    // readFile :: FilePath -> IO String
+    const readFile = fp => {
+        const
+            e = $(),
+            uw = ObjC.unwrap,
+            s = uw(
+                $.NSString.stringWithContentsOfFileEncodingError(
+                    $(fp)
+                    .stringByStandardizingPath,
+                    $.NSUTF8StringEncoding,
+                    e
+                )
+            );
+        return undefined !== s ? (
+            s
+        ) : uw(e.localizedDescription);
+    };
+
+    // showLog :: a -> IO ()
+    const showLog = (...args) =>
+        console.log(
+            args
+            .map(JSON.stringify)
+            .join(' -> ')
+        );
+
+    // MAIN ---
+    return main();
+})();