Data commit

Task/Range-expansion/JavaScript/range-expansion-4.js

@@ -0,0 +1,64 @@
+(() => {
+    "use strict";
+
+    // ----------------- RANGE EXPANSION -----------------
+
+    // rangeExpansion :: String -> [Int]
+    const rangeExpansion = rangeString =>
+        // A list of integers parsed from a
+        // comma-delimited string which may include
+        // (rising) hyphenated ranges.
+        rangeString.split(",")
+        .flatMap(x => {
+            const ns = x.split("-")
+                .reduce((a, s, i, xs) =>
+                    Boolean(s) ? (
+                        0 < i ? a.concat(
+                            parseInt(
+                                xs[i - 1].length ? (
+                                    s
+                                ) : `-${s}`,
+                                10
+                            )
+                        ) : [Number(s)]
+                    ) : a,
+                    []
+                );
+
+            return 2 === ns.length ? (
+                uncurry(enumFromTo)(ns)
+            ) : ns;
+        });
+
+
+    // ---------------------- TEST -----------------------
+    // main :: IO ()
+    const main = () =>
+        rangeExpansion("-6,-3--1,3-5,7-11,14,15,17-20");
+
+
+    // --------------------- GENERIC ---------------------
+
+    // enumFromTo :: Int -> Int -> [Int]
+    const enumFromTo = m =>
+        n => Array.from({
+            length: 1 + n - m
+        }, (_, i) => m + i);
+
+
+    // uncurry :: (a -> b -> c) -> ((a, b) -> c)
+    const uncurry = f =>
+        // A function over a pair, derived
+        // from a curried function.
+        (...args) => {
+            const [x, y] = Boolean(args.length % 2) ? (
+                args[0]
+            ) : args;
+
+            return f(x)(y);
+        };
+
+
+    // MAIN ---
+    return JSON.stringify(main());
+})();