Add tasks for all the new languages

Task/Combinations/Sidef/combinations-1.sidef

@@ -0,0 +1 @@
+(@^5).combinations(3, {|c| say c })

Task/Combinations/Sidef/combinations-2.sidef

@@ -0,0 +1,17 @@
+func combine(n, set) {
+
+    set.len || return []
+    n == 1  && return set.map{[_]}
+
+    var (head, result)
+    head   = set.shift
+    result = combine(n-1, [set...])
+
+    for subarray in result {
+        subarray.prepend(head)
+    }
+
+    result + combine(n, set)
+}
+
+combine(3, @^5).each {|c| say c }

Task/Combinations/Sidef/combinations-3.sidef

@@ -0,0 +1,31 @@
+func forcomb(callback, n, k) {
+
+    if (k == 0) {
+        callback([])
+        return()
+    }
+
+    if (k<0 || k>n || n==0) {
+        return()
+    }
+
+    var c = @^k
+
+    loop {
+        callback([c...])
+        c[k-1]++ < n-1 && next
+        var i = k-2
+        while (i>=0 && c[i]>=(n-(k-i))) {
+            --i
+        }
+        i < 0 && break
+        c[i]++
+        while (++i < k) {
+            c[i] = c[i-1]+1
+        }
+    }
+
+    return()
+}
+
+forcomb({|c| say c }, 5, 3)