2016 Update

Task/List-comprehensions/JavaScript/list-comprehensions-1.js

@@ -1,14 +1,32 @@
-function range(begin, end) {
-    for (let i = begin; i < end; ++i)
-        yield i;
-}
+// USING A LIST MONAD DIRECTLY, WITHOUT SPECIAL SYNTAX FOR LIST COMPREHENSIONS
 
-function triples(n) {
-    return [[x,y,z] for each (x in range(1,n+1))
-                     for each (y in range(x,n+1))
-                     for each (z in range(y,n+1))
-                     if (x*x + y*y == z*z) ]
-}
+(function (n) {
 
-for each (var triple in triples(20))
-    print(triple);
+    return mb(r(1,     n), function (x) {  // x <- [1..n]
+    return mb(r(1 + x, n), function (y) {  // y <- [1+x..n]
+    return mb(r(1 + y, n), function (z) {  // z <- [1+y..n]
+
+       return x * x + y * y === z * z ? [[x, y, z]] : [];
+
+    })})});
+
+
+    // LIBRARY FUNCTIONS
+
+    // Monadic bind for lists
+    function mb(xs, f) {
+        return [].concat.apply([], xs.map(f));
+    }
+
+    // Monadic return for lists is simply lambda x -> [x]
+    // as in [[x, y, z]] : [] above
+
+    // Integer range [m..n]
+    function r(m, n) {
+        return Array.apply(null, Array(n - m + 1))
+            .map(function (n, x) {
+                return m + x;
+            });
+    }
+
+})(100);