- Added the Array.sort_by{} method, which sorts an array by a specifi…

…c value.

Example:
	[4,3,1,2].sort_by { _ };	    # same as .sort();
	[4,3,1,2].sort_by {|n| -n };        # reverse sorting
	%w(foo fo f).sort_by { .len } 	    # sort array by length

- Added two new Sidef scripts.

MANIFEST

@@ -393,6 +393,8 @@ scripts/RosettaCode/inheritance_single.sf
 scripts/RosettaCode/knapsack_problem_continuous.sf
 scripts/RosettaCode/largest_int_from_concatenated_ints.sf
 scripts/RosettaCode/last_sunday_of_each_month.sf
+scripts/RosettaCode/left_factorials.sf
+scripts/RosettaCode/left_factorials_1.sf
 scripts/RosettaCode/levenshtein_distance.sf
 scripts/RosettaCode/levenshtein_distance_1.sf
 scripts/RosettaCode/levenshtein_distance_2.sf

lib/Sidef/Types/Array/Array.pm

@@ -1106,6 +1106,11 @@ package Sidef::Types::Array::Array {
         $self->new(sort { $a cmp $b } @{$self});
     }
 
+    sub sort_by {
+        my ($self, $code) = @_;
+        $self->new(map { $_->[0] } sort { $a->[1] cmp $b->[1] } map { [$_, $code->run($_)] } @{$self});
+    }
+
     sub cmp {
         my ($self, $arg) = @_;
 

lib/Sidef/Types/Array/Array.pod

@@ -813,6 +813,14 @@ Return the
 
 =cut
 
+=head2 sort_by
+
+Array.sort_by() -> I<Obj>
+
+Return the
+
+=cut
+
 =head2 splice
 
 Array.splice() -> I<Obj>

scripts/RosettaCode/left_factorials.sf

@@ -0,0 +1,15 @@
+#!/usr/bin/ruby
+
+#
+## http://rosettacode.org/wiki/Left_factorials#Sidef
+#
+
+func left_fact(k) {
+    range(0, k-1).map { _! }.sum \\ 0;
+}
+
+[range(0, 10), range(20, 50).by(10)].each { |r|
+    r.each { |i|
+        printf("!%d  = %s\n", i, left_fact(i));
+    }
+}

scripts/RosettaCode/left_factorials_1.sf

@@ -0,0 +1,30 @@
+#!/usr/bin/ruby
+
+#
+## http://rosettacode.org/wiki/Left_factorials#Sidef
+#
+
+func left_fact(n) {
+    static cached    = 0;
+    static factorial = 1;
+    static leftfact  = 0;
+
+    if (n < cached) {
+        cached    = 0;
+        factorial = 1;
+        leftfact  = 0;
+    }
+
+    while (n > cached) {
+        leftfact  += factorial;
+        factorial *= ++cached;
+    }
+
+    leftfact;
+}
+
+[range(0, 10), range(20, 50).by(10)].each { |r|
+    r.each { |i|
+        printf("!%d  = %s\n", i, left_fact(i));
+    }
+}