Introducing EmptySeq constant

- The Empty Sequence (we only need one of them)
- use EmptySeq in setting where possible

Empty sequences in Any-iterable-methods and Str where too soon in the setting.
Please revert if having an EmptySeq constant is a bad idea.

src/core/IO/CatHandle.pm

@@ -115,7 +115,8 @@ my class IO::CatHandle is IO::Handle {
           nqp::while(
             nqp::defined(self.next-handle),
             take $!active-handle.words)}),
-        Seq.new: Rakudo::Iterator.Empty)
+        EmptySeq
+      )
     }
     multi method words(::?CLASS:D \SELF: $limit, :$close) {
         nqp::istype($limit,Whatever) || $limit == Inf
@@ -140,7 +141,8 @@ my class IO::CatHandle is IO::Handle {
           nqp::while(
             nqp::defined(self.next-handle),
             take $!active-handle.lines)}),
-        Seq.new: Rakudo::Iterator.Empty)
+        EmptySeq
+      )
     }
     multi method lines(::?CLASS:D \SELF: $limit, :$close) {
         nqp::istype($limit,Whatever) || $limit == Inf

src/core/IO/Spec/Unix.pm

@@ -104,7 +104,7 @@ my class IO::Spec::Unix is IO::Spec {
             nqp::until(
               nqp::iseq_i($els, $i = nqp::add_i($i, 1)),
               take nqp::atpos($parts, $i) || '.')
-        } !! Seq.new: Rakudo::Iterator.Empty
+        } !! EmptySeq
     }
 
     method splitpath( $path, :$nofile = False ) {

src/core/Mixy.pm

@@ -43,7 +43,7 @@ my role Mixy does Baggy  {
       nqp::if(
         (my $total := self!total-positive),
         self.roll($calculate($total)),
-        Seq.new(Rakudo::Iterator.Empty)
+        EmptySeq
       )
     }
     multi method roll(Mixy:D: $count) {

src/core/Range.pm

@@ -502,7 +502,7 @@ my class Range is Cool does Iterable does Positional {
               !! self.list.roll(*)
         }
         else {
-            Seq.new(Rakudo::Iterator.Empty)
+            EmptySeq
         }
     }
     multi method roll(Range:D:) {
@@ -547,7 +547,7 @@ my class Range is Cool does Iterable does Positional {
               !! self.list.roll($todo)
         }
         else {
-            Seq.new(Rakudo::Iterator.Empty)
+            EmptySeq
         }
     }
 
@@ -556,7 +556,7 @@ my class Range is Cool does Iterable does Positional {
     multi method pick(Whatever)  {
         self.elems
           ?? self.list.pick(*)
-          !! Seq.new(Rakudo::Iterator.Empty)
+          !! EmptySeq
     }
     multi method pick(Int(Cool) $todo) {
         if self.elems -> $elems {
@@ -606,7 +606,7 @@ my class Range is Cool does Iterable does Positional {
               !! self.list.pick($todo)
         }
         else {
-            Seq.new(Rakudo::Iterator.Empty)
+            EmptySeq
         }
     }
 

src/core/Seq.pm

@@ -340,4 +340,10 @@ multi sub infix:<eqv>(Seq:D \a, Seq:D \b) {
     )
 }
 
+# The Empty Sequence
+my constant EmptySeq = nqp::p6bindattrinvres(
+  nqp::create( class EmptySeq is Seq {
+      method iterator() { nqp::getattr(self,Seq,'$!iter') }
+  }),Seq,'$!iter',Rakudo::Iterator.Empty);
+
 # vim: ft=perl6 expandtab sw=4