Add Palindromic Number in Elvish (#4291)

Author: Kaamkiya

archive/e/elvish/palindromic-number.elv

@@ -0,0 +1,33 @@
+use str
+
+fn die {
+  echo 'Usage: please input a non-negative integer'
+  exit 1
+}
+
+if (> 1 (count $args)) {
+  die
+}
+
+var n = $args[0]
+
+# Check if the number contains a decimal point
+if (str:contains $n .) {
+  die
+}
+
+try {
+  var q = (+ $n 1)
+} catch _ {
+  die
+}
+
+if (> 0 $n) {
+  die
+}
+
+if (eq $n (echo $n|rev)) {
+  echo true
+} else {
+  echo false
+}