first shot at "lazy" statement prefix

rakudo · May 16, 2012 · 18f9e41 · 18f9e41
1 parent f4e6701
commit 18f9e41
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Showing 5 changed files with 31 additions and 0 deletions.
diff --git a/src/Perl6/Actions.pm b/src/Perl6/Actions.pm
@@ -901,6 +901,10 @@ class Perl6::Actions is HLL::Actions {
     method statement_prefix:sym<PRE>($/)   { make $*W.add_phaser($/, 'PRE', ($<blorst>.ast)<code_object>, ($<blorst>.ast)<past_block>); }
     method statement_prefix:sym<POST>($/)  { make $*W.add_phaser($/, 'POST', ($<blorst>.ast)<code_object>, ($<blorst>.ast)<past_block>); }
 
+    method statement_prefix:sym<lazy>($/) {
+        make $*W.create_lazy($/, $<blorst>.ast()<code_object>);
+    }
+
     method statement_prefix:sym<DOC>($/)   {
         $*W.add_phaser($/, ~$<phase>, ($<blorst>.ast)<code_object>)
             if %*COMPILING<%?OPTIONS><doc>;

diff --git a/src/Perl6/Grammar.pm b/src/Perl6/Grammar.pm
@@ -874,6 +874,7 @@ grammar Perl6::Grammar is HLL::Grammar {
     token statement_prefix:sym<try>   { <sym> <blorst> }
     token statement_prefix:sym<gather>{ <sym> <blorst> }
     token statement_prefix:sym<do>    { <sym> <blorst> }
+    token statement_prefix:sym<lazy>  { <sym> <blorst> }
     token statement_prefix:sym<DOC>   {
         <sym> \s <.ws> $<phase>=['BEGIN' || 'CHECK' || 'INIT']
         <blorst>

diff --git a/src/Perl6/World.pm b/src/Perl6/World.pm
@@ -590,6 +590,13 @@ class Perl6::World is HLL::World {
         self.finish_code_object($code, $code_past, $is_dispatcher, :yada($yada));
         $code
     }
+
+    method create_lazy($/, $code) {
+        my $type      := self.find_symbol(['LazyScalar']);
+        my $container := $type.new($code);
+        self.add_object($container);
+        self.get_ref($container);
+    }
 
     # Stubs a code object of the specified type.
     method stub_code_object($type) {

diff --git a/src/core/LazyScalar.pm b/src/core/LazyScalar.pm
@@ -0,0 +1,18 @@
+my class LazyScalar is Proxy {
+    method new($code) {
+        my int $reified = 0;
+        my Mu $payload;
+        self.Proxy::new(
+            FETCH => sub ($) {
+                unless $reified {
+                    $payload := $code();
+                    $reified = 1;
+                } 
+                $payload;
+            },
+            STORE => sub ($, Mu \$new) {
+                $payload := $new;
+            }
+        )
+    }
+}
diff --git a/tools/build/Makefile.in b/tools/build/Makefile.in
@@ -232,6 +232,7 @@ CORE_SOURCES = \
   src/core/operators.pm \
   src/core/metaops.pm \
   src/core/terms.pm \
+  src/core/LazyScalar.pm \
   src/core/NYI.pm \
   src/core/you_are_here.pm \