Add take and drop functions for list library (#386)

* Add take and drop

* Small change to scss file

Author: remo5000

public/externalLibs/list.js

@@ -373,6 +373,24 @@ function set_tail(xs,x) {
     }
 }
 
+// take(xs, n) puts the first n elements of xs into a list.
+function take(xs, n) {
+    if (n < 0) {
+        throw new Error("take(xs, n) expects a positive integer as " +
+            "argument n, but encountered " + n);
+    }
+    return (n === 0) ? [] : pair(head(xs), take(tail(xs), n - 1));
+}
+
+// drop(xs, n) removes the first n elements from xs and returns the rest (as a list)
+function drop(xs, n) {
+    if (n < 0) {
+        throw new Error("drop(xs, n) expects a positive integer as " +
+            "argument n, but encountered " + n);
+    }
+    return (n === 0) ? xs : drop(tail(xs), n - 1);
+}
+
 //function display(str) {
 //	var to_show = str;
 //    if (is_array(str) && str.length > 2) {

src/styles/_academy.scss

@@ -226,12 +226,12 @@
   text-align: left;
 }
 
-md th,
-td {
+.md th,
+.md td {
   text-align: left;
   padding: 8px;
 }
 
-md tr:nth-child(even) {
+.md tr:nth-child(even) {
   background-color: #f2f2f2;
 }