Add tasks for all the new languages

Task/Long-multiplication/Sidef/long-multiplication-1.sidef

@@ -0,0 +1 @@
+say (2**64 * 2**64);

Task/Long-multiplication/Sidef/long-multiplication-2.sidef

@@ -0,0 +1,37 @@
+func add_with_carry(result, addend, addendpos) {
+    loop {
+        while (result.len < addendpos+1) {
+            result.append(0);
+        };
+        var addend_digits = (addend.to_i + result[addendpos].to_i -> to_chars);
+        result[addendpos] = addend_digits.pop;
+        addend_digits.len > 0 || break;
+        addend = addend_digits.pop;
+        addendpos++;
+    }
+}
+
+func longhand_multiplication(multiplicand, multiplier) {
+
+    var result = [];
+    var multiplicand_offset = 0;
+
+    multiplicand.reverse.each { |multiplicand_digit|
+        var multiplier_offset = multiplicand_offset;
+        multiplier.reverse.each { |multiplier_digit|
+            var multiplication_result = (multiplicand_digit.to_i * multiplier_digit.to_i -> to_s);
+
+            var addend_offset = multiplier_offset;
+            multiplication_result.reverse.each { |result_digit_addend|
+                add_with_carry(result, result_digit_addend, addend_offset);
+                addend_offset++;
+            };
+            multiplier_offset++;
+        };
+        multiplicand_offset++;
+    };
+
+    return result.join.reverse;
+}
+
+say longhand_multiplication('18446744073709551616', '18446744073709551616');

Task/Long-multiplication/Sidef/long-multiplication-3.sidef

@@ -0,0 +1,50 @@
+func long_multiplication(String a, String b) -> String {
+
+    if (a.len < b.len) {
+        (a, b) = (b, a)
+    }
+
+    '0' ~~ [a, b] && return '0'
+
+    var x = a.reverse.chars.map{.to_n}
+    var y = b.reverse.chars.map{.to_n}
+
+    var xlen = x.end
+    var ylen = y.end
+
+    var mem = 0
+    var map = y.len.of { [] }
+
+    for j in ^y {
+        for i in ^x {
+            var n = (x[i]*y[j] + mem)
+            var(d, m) = n.divmod(10)
+            if (i == xlen) {
+                map[j] << (m, d)
+                mem = 0;
+            }
+            else {
+                map[j] << m
+                mem = d
+            }
+        }
+
+        var n = (ylen - j)
+        n > 0 && map[j].append(n.of(0)...)
+        var m = (ylen - n)
+        m > 0 && map[j].prepend(m.of(0)...)
+    }
+
+    var result = []
+    var mrange = ^map
+    var end    = (xlen + ylen + 2)
+
+    for i in ^end {
+        var n = (mrange.map {|j| map[j][i] }.sum + mem)
+        (mem, result[result.end+1]) = n.divmod(10)
+    }
+
+    result.join.reverse -= /^0+/
+}
+
+say long_multiplication('18446744073709551616', '18446744073709551616')