From: Matt S Trout <mst@shadowcat.co.uk>
Date: Wed, 16 Jul 2008 18:42:28 +0000 (+0000)
Subject: exprs
X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=commitdiff_plain;h=abd9923dbfb7872e028fd7ead878c0b4fbf10d8b;p=dbsrgits%2FSQL-Abstract.git

exprs
---

diff --git a/e.pl b/e.pl
new file mode 100644
index 0000000..60c2414
--- /dev/null
+++ b/e.pl
@@ -0,0 +1,94 @@
+use strict;
+use warnings;
+
+{
+  package E;
+  
+  use overload
+    '==' => '_op_num_eq',
+    '>' => '_op_num_gt',
+  ;
+  
+  sub new {
+    my ($self, $data) = @_;
+    my $class = ref($self) || $self;
+    return bless(\$data, $class);
+  };
+  
+  sub _op_num_eq { shift->_binop('==', @_) };
+  sub _op_num_gt { shift->_binop('>', @_) };
+  
+  sub _binop {
+    my ($self, $op, $rhs) = @_;
+    $self->new([
+      $op,
+      ${$self},
+      (ref $rhs ? ${$rhs} : [ -value, $rhs ]),
+    ]);
+  };
+  
+  package I;
+  
+  sub AUTOLOAD {
+    our $AUTOLOAD =~ s/.*:://;
+    return I::E->new([ -name, $AUTOLOAD ]);
+  }
+
+  sub DESTROY { }
+  
+  package I::E;
+  
+  our @ISA = qw(I E);
+  
+  1;
+}
+
+use Data::Dump qw(dump);
+use Scalar::Util qw(blessed);
+
+sub _une {
+  my $un = shift;
+  blessed($un) && $un->isa('E')
+    ? ${$un}
+    : ref($un) eq 'ARRAY'
+      ? [ map { _une($_) } @$un ]
+      : $un;
+}
+
+sub _run_e {
+  local $_ = bless(\do { my $x }, 'I');
+  map { _une($_) } $_[0]->();
+}
+
+sub expr (&) { _run_e(@_) }
+sub _do {
+  my ($name, $code, @in) = @_;
+  [ $name, _run_e($code), @in ];
+}
+sub _dolist {
+  my ($name, $code, @in) = @_;
+  _do($name, sub { [ -list, map { _une($_) } $code->() ] }, @in);
+}
+sub ORDER_BY (&;@) { _do(-order_by, @_) }
+sub SELECT (&;@) { _dolist('-select', @_); }
+sub JOIN (&;@) { _do('-join', @_) }
+sub WHERE (&;@) { _do(-where, @_) }
+sub GROUP_BY (&;@) { _dolist(-group_by, @_); }
+sub sum { E->new([ -sum, _une(shift) ]); }
+
+#warn dump(expr { $_->one == $_->two });
+warn dump(
+  ORDER_BY { $_->aggregates->total }
+    SELECT { $_->users->name, $_->aggregates->total }
+      JOIN { $_->users->id == $_->aggregates->recipient_id }
+        [ users => expr { $_->users } ],
+        [ aggregates =>
+            expr {
+                SELECT { $_->recipient_id, [ total => sum($_->commission) ] }
+                 WHERE { sum($_->commission) > 500 }
+              GROUP_BY { $_->recipient_id }
+                 WHERE { $_->entry_date > '2007-01-01' }
+                  expr { $_->commissions }
+            }
+        ]
+);