First cut of WALK; doesn't know all of the various orderings, but kno…

…ws how to handle canonical and super.

src/setting/Object.pm

@@ -1,3 +1,5 @@
+subset Matcher of Object where { $_.can('ACCEPTS') };
+
 class Object is also {
     multi method perl {
         self.WHAT.substr(0, -2) ~ '.new()';
@@ -6,6 +8,100 @@ class Object is also {
     multi method eigenstates {
         list(self)
     }
+
+    method WALK(:$name!, :$canonical, :$ascendant, :$descendant, :$preorder, :$breadth,
+                :$super, Matcher :$omit, Matcher :$include) {
+        # First, build list of classes in the order we'll need them.
+        my @classes;
+        if $super {
+            @classes = self.^isa();
+        } else {
+            if $breadth {
+                die ":breadth unimplemented";
+            } elsif $ascendant {
+                die ":ascendant unimplemented";
+            } elsif $descendant {
+                die ":descendant unimplemented";
+            } elsif $preorder {
+                die ":preorder unimplemented";
+            } else {
+                # Canonical, the default.
+                my sub merge_c3(@to_merge) {
+                    my $accepted;
+                    my $found = 0;
+                    my $cand_count = 0;
+                    loop (my $i = 0; $i < +@to_merge; $i++) {
+                        if +@to_merge[$i] {
+                            $cand_count++;
+                            my $cand_class = @to_merge[$i][0];
+                            my $reject = False;
+                            loop (my $j = 0; $j < +@to_merge; $j++) {
+                                if $i != $j {
+                                    loop (my $k = 1; $k < +@to_merge[$j]; $k++) {
+                                        if @to_merge[$j][$k].WHAT =:= $cand_class.WHAT {
+                                            $reject = True;
+                                            last;
+                                        }
+                                    }
+                                }
+                            }
+                            unless $reject {
+                                $accepted = $cand_class;
+                                $found = 1;
+                                last;
+                            }
+                        }
+                    }
+                    if !$cand_count {
+                        return ();
+                    }
+                    if !$found {
+                        die "Could not build C3 linearization: ambiguous hierarchy";
+                    }
+                    for @to_merge -> @cur_list is rw {
+                        @cur_list .= grep({ $^class.WHAT !=:= $accepted.WHAT });
+                    }
+                    my @result = merge_c3(@to_merge);
+                    unshift @result, $accepted;
+                    return @result;
+                }
+                my sub compute_c3($class) {
+                    my @immediates = $class.^isa();
+                    if @immediates.elems == 0 {
+                        @classes = $class;
+                    } else {
+                        my @to_merge = @immediates.map({ [compute_c3($^parent)] });
+                        push @to_merge, [@immediates];
+                        my @merged = merge_c3(@to_merge);
+                        unshift @merged, $class;
+                        return @merged;
+                    }
+                }
+                @classes = compute_c3(self.WHAT());
+            }
+        }
+
+        # Filter as needed.
+        if $omit {
+            @classes .= grep { !$omit.ACCEPTS($_) };
+        }
+        if $include {
+            @classes .= grep { !$include.ACCEPTS($_) };
+        }
+
+        # Now we have classes, build method list.
+        my @methods;
+        for @classes -> $class {
+            for $class.^methods() -> $method {
+                my $check_name = $method.?name;
+                if $check_name.defined && $check_name eq $name {
+                    @methods.push($method);
+                }
+            }
+        }
+
+        return @methods;
+    }
 }
 
 # vim: ft=perl6