BackCode implies TwoWay and DefaultFlow

Author: mohawk2

Changes

@@ -9,6 +9,7 @@
 - MatrixOps::svd now handles transpose transparently
 - all ops with two-way dataflow now work as lvalues
 - AffinePriv now implies TwoWay and P2Child
+- BackCode (including from EquivCPOffsCode) now implies TwoWay and DefaultFlow
 
 2.103 2026-03-03
 - fix regression in *linvals so takes ndarrays as start and end again

lib/PDL/MatrixOps.pd

@@ -1308,8 +1308,6 @@ EOT
 );
 
 pp_def('mstack',
-  DefaultFlow => 1,
-  TwoWay => 1,
   Pars => 'x(n,m);y(n,p);[o]out(n,q=CALC($SIZE(m)+$SIZE(p)));',
   GenericTypes => [ppdefs_all()],
   Code => '
@@ -1332,8 +1330,6 @@ EOT
 );
 
 pp_def('augment',
-  DefaultFlow => 1,
-  TwoWay => 1,
   Pars => 'x(n); y(p);[o]out(q=CALC($SIZE(n)+$SIZE(p)))',
   GenericTypes => [ppdefs_all()],
   Code => '

lib/PDL/Ops.pd

@@ -412,8 +412,6 @@ PDL_IF_BAD(if ( \$ISBAD(complexv()) ) \$SETBAD(b()); else,)
   $codestr
 	   }),
 	   !$backcode ? () : (
-	     DefaultFlow => 1,
-	     TwoWay => 1,
 	     BackCode => pp_line_numbers(__LINE__-1, qq{
 		PDL_IF_BAD(if ( \$ISBAD(b()) ) \$SETBAD(complexv()); else {,)
 		   $backcode

lib/PDL/PP.pm

@@ -1058,7 +1058,7 @@ my $pars_re = $PDL::PP::PdlParObj::pars_re;
 $PDL::PP::deftbl =
   [
    PDL::PP::Rule->new(
-      [qw(RedoDims EquivCPOffsCode HandleBad P2Child TwoWay)],
+      [qw(RedoDims EquivCPOffsCode HandleBad P2Child)],
       ["Identity"],
       "something to do with dataflow between CHILD & PARENT, I think.",
       sub {
@@ -1077,7 +1077,7 @@ $PDL::PP::deftbl =
              for(i=0; i<$PDL(CHILD)->nvals; i++)  {
                 $EQUIVCPOFFS(i,i);
              }'),
-        1, 1, 1);
+        1, 1);
       }),
 
    # used as a flag for many of the routines
@@ -1485,6 +1485,8 @@ EOF
      }),
    PDL::PP::Rule::Returns->new("OverloadDocValues", []),
 
+   PDL::PP::Rule::Returns::One->new('TwoWay', 'BackCode', 'BackCode => TwoWay'),
+   PDL::PP::Rule::Returns::One->new('DefaultFlow', 'BackCode', 'BackCode => DefaultFlow'),
    PDL::PP::Rule::Returns::One->new('TwoWay', 'AffinePriv', 'AffinePriv => TwoWay'),
    PDL::PP::Rule::Returns->new("TwoWayFlag", "TwoWay", "PDL_ITRANS_TWOWAY"),
    PDL::PP::Rule::Returns::Zero->new("TwoWayFlag"),

lib/PDL/PP.pod

@@ -2611,6 +2611,7 @@ If I<set>, sets in the C<pdl_transvtable> (see L<PDL::Internals>) the
 C<iflags> such that the trans will start with dataflow both forwards
 and backwards. Note that setting this to any value (including 0) will
 trigger the behaviour.
+As of 2.104, implied by C<BackCode> (including from C<EquivCPOffsCode>).
 
 =head3 HaveBroadcasting
 
@@ -2629,7 +2630,8 @@ first argument's C<copy> method will be used.
 If true, sets in the C<pdl_transvtable> (see L<PDL::Internals>) the
 C<iflags> such as to inform the trans's error checks connected to dataflow.
 As of 2.104, also automatically sets C<Lvalue>.
-As of 2.104, implied by C<AffinePriv>.
+As of 2.104, implied by C<AffinePriv> and C<BackCode> (including
+from C<EquivCPOffsCode>).
 
 =head3 Identity
 
@@ -2640,6 +2642,7 @@ C<TwoWay> such that the function is a dataflowing identity transformation.
 
 For dataflowing functions, this value (which gets parsed) overrides the
 operation of that from children ndarrays to parents.
+As of 2.104, implies C<TwoWay> and C<DefaultFlow>.
 
 =head3 BadBackCode
 

lib/PDL/Slices.pd

@@ -149,8 +149,6 @@ my $index_init =
 pp_def('index',
        GenericTypes => [ppdefs_all],
        HandleBad => 1,
-       DefaultFlow => 1,
-       TwoWay => 1,
        Pars => 'a(n); indx ind(); [oca] c();',
        Code =>
        $index_init . ' $c() = $a(n => this_ind);',
@@ -164,8 +162,6 @@ pp_def('index',
 pp_def('index1d',
        GenericTypes => [ppdefs_all],
        HandleBad => 1,
-       DefaultFlow => 1,
-       TwoWay => 1,
        Pars => 'a(n); indx ind(m); [oca] c(m);',
        Code => pp_line_numbers(__LINE__, <<'EOF'),
          loop(m) %{
@@ -212,8 +208,6 @@ EOF
 pp_def('index2d',
        GenericTypes => [ppdefs_all],
        HandleBad => 1,
-       DefaultFlow => 1,
-       TwoWay => 1,
        Pars => 'a(na,nb); indx inda(); indx indb(); [oca] c();',
        Code =>
        $index2d_init . pp_line_numbers(__LINE__-1, ' $c() = $a(na => this_ind_a, nb => this_ind_b);'),
@@ -578,7 +572,6 @@ parameters.  C<rangeb> is marginally faster as it makes a direct PP call,
 avoiding the perl argument-parsing step.
 EOD
         HandleBad => 1,
-        TwoWay => 1,
         P2Child => 1,
 
 # rdim: dimensionality of each range (0 dim of index PDL)
@@ -1405,7 +1398,6 @@ EOF
                         $EQUIVCPOFFS(i,i);
                 }
 EOF
-        TwoWay => 1,
         Doc => 'internal',
 );
 
@@ -1816,8 +1808,6 @@ pp_def('rotate',
         GenericTypes => [ppdefs_all],
         Doc => 'Shift vector elements along with wrap.',
         Pars=>'x(n); indx shift(); [oca]y(n)',
-        DefaultFlow => 1,
-        TwoWay => 1,
         RedoDimsCode=>'if ($SIZE(n) == 0) $CROAK("can not shift zero size ndarray");',
         Code=>$rotate_code.'
             $y(n=>j++) = $x();