add specifications and fix examples for current rakudo

perlmonks/combinations-731808.pl

@@ -1,14 +1,31 @@
 use v6;
 
+# Specification:
+#    From http://www.perlmonks.org/?node_id=731808
+#    Given a list of URL prefixes, and a list of product IDs, make a list
+#    consisting of each URL prefix concatenated with each product ID.
+
+
 my @urls = ('http://www.something.com/blah.aspx?code=',
             'http://www.somethingelse.com/stuff.aspx?thing=');
 
 my @ids = <375035304 564564774 346464646>;
 
-my @combined = (@urls X @ids).map: {$^a ~ $^b};
+
+# 1. Cross then map
+# We use the cross operator X to make every combination of pairs from @urls
+# and @ids. We then use map to stringify each pair. $^a is a "placeholder
+# argument" - in this case, it refers to the only argument to the block.
+my @combined = (@urls X @ids).map: { ~$^a };
 
 .say for @combined;
 
-# or even easier with the cross-meta operator:
 
-# .say for @urls X~ @ids;
+# 2. cross hyperoperator
+# We use the cross hyperoperator X~
+# This combines each element from list1 with each element from list2 using ~
+#    You can use any infix operator.
+#    Try (1,2,3) X* (1,2,3) to generate a multiplication table.
+
+
+.say for @urls X~ @ids;

perlmonks/weighted-roll-731696.pl

@@ -1,24 +1,52 @@
 use v6;
 
+# Specification:
+#   From http://www.perlmonks.org/?node_id=731443
+#   This is part of a strategy game. There are a number of ships in combat,
+#   and you must determine which order they get to take their actions.
+#     * Each ship has an initiative value.
+#     * At the start of the turn, each ship gets a number of ballots equal to
+#       their initiative. The ballots are drawn out randomly. The first time a
+#       ship's ballot gets drawn, it takes its turn. The rest of its ballots
+#       are wasted.
+#
+# Worked example:
+# 3 ships <A B C> with initiative (1,2,4).
+# We put ballots into an array: <A B B C C C C>
+# We draw a ballot out at random: C. C takes its turn.
+# We draw another ballot:  C. do nothing.
+# We draw another ballot:  C. do nothing.
+# We draw another ballot:  B. B takes its turn.
+# We draw another ballot:  B. do nothing.
+# We draw another ballot:  A. A takes its turn.
+# We draw the last ballot: C. do nothing.
+# So the final order is: <C B A>
+# This is not necessarily the most efficient way to perform the algorithm.
+
+
+# Useful things to note:
+# to generate a random number from 1 to N, use (1..N).pick
+# to generate a random number from 0 to N-1, use (0..^N).pick
+
 our $SHIPS = 4;
 our $REPS  = 30;
 
-my @weights = list(1..$SHIPS).map: { 1+16.rand.int };
+my @weights = (1..16).pick($SHIPS, :replace);
 for @weights.kv -> $k, $v { say "$k: $v" }
 
 my $total = [+] @weights;
 say "Total Weights $total";
 
 sub pick (@weights, $total) {
-   my $rand = $total.rand.int;
+   #my $rand = $total.rand.int;
+   my $rand = (0..^$total).pick;
    for @weights.kv -> $i, $w {
        $rand -= $w;
        return $i if $rand < 0;
    }
 }
 
-sub pickAll (@w,$t) {
-   my @weights = @w.clone; my $total = $t.clone;  #a hack until "is copy" gets implemented
+sub pickAll (@weights is copy, $total is copy) {
    my @order;
    for @weights {
         my $pick = pick(@weights, $total);
@@ -29,7 +57,7 @@ (@w,$t)
    return @order;
  }
 
-pickAll(@weights,$total).join.say for 1 .. $REPS;
+say ~pickAll(@weights,$total) for 1 .. $REPS;