Data update

Task/Roman-numerals-Decode/JavaScript/roman-numerals-decode-8.js

@@ -1,6 +1,7 @@
 (() => {
+    "use strict";
 
-    // -------------- ROMAN NUMERALS DECODED ---------------
+    // ------------- ROMAN NUMERALS DECODED --------------
 
     // Folding from right to left,
     // lower leftward characters are subtracted,
@@ -8,49 +9,34 @@
 
     // fromRoman :: String -> Int
     const fromRoman = s =>
-        foldr(l => ([r, n]) => [
-            l,
-            l >= r ? (
-                n + l
-            ) : n - l
-        ])([0, 0])(
-            [...s].map(charVal)
+        [...s]
+        .map(glyphValue)
+        .reduceRight(
+            ([r, n], l) => [
+                l,
+                l >= r
+                    ? n + l
+                    : n - l
+            ],
+            [0, 0]
         )[1];
 
-    // charVal :: Char -> Maybe Int
-    const charVal = k => {
-        const v = {
-            I: 1,
-            V: 5,
-            X: 10,
-            L: 50,
-            C: 100,
-            D: 500,
-            M: 1000
-        } [k];
-        return v !== undefined ? v : 0;
-    };
 
-    // ----------------------- TEST ------------------------
-    const main = () => [
-            'MDCLXVI', 'MCMXC', 'MMVIII', 'MMXVI', 'MMXVII'
-        ]
-        .map(fromRoman)
-        .join('\n');
+    // glyphValue :: Char -> Maybe Int
+    const glyphValue = k => ({
+        I: 1,
+        V: 5,
+        X: 10,
+        L: 50,
+        C: 100,
+        D: 500,
+        M: 1000
+    }) [k] || 0;
 
-
-    // ----------------- GENERIC FUNCTIONS -----------------
-
-    // foldr :: (a -> b -> b) -> b -> [a] -> b
-    const foldr = f =>
-        // Note that that the Haskell signature of foldr
-        // differs from that of foldl - the positions of
-        // accumulator and current value are reversed.
-        a => xs => [...xs].reduceRight(
-            (a, x) => f(x)(a),
-            a
-        );
-
-    // MAIN ---
-    return main();
+    // ---------------------- TEST -----------------------
+    return [
+        "MDCLXVI", "MCMXC", "MMVIII", "MMXVI", "MMXVII"
+    ]
+    .map(fromRoman)
+    .join("\n");
 })();