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Objectify: warn if Is{Component,Positional}ObjectRep absent #4964

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8c9d090
Objectify: warn if Is{Component,Positional}ObjectRep absent
fingolfin Jul 29, 2022
d1171f7
Fix bug
fingolfin Jan 8, 2025
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3 changes: 2 additions & 1 deletion lib/alglie.gi
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Original file line number Diff line number Diff line change
Expand Up @@ -3975,7 +3975,8 @@ InstallMethod( NormalizedElementOfMagmaRingModuloRelations,
Append( tlist, todo[i] );
od;

return ObjByExtRep( Fam, [ zero, tlist ] );
tlist := ObjByExtRep( Fam, [ zero, tlist ] );
return [ zero, tlist![2] ];

@ThomasBreuer ThomasBreuer Jun 8, 2026

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As far as I see, this change is a bugfix.
(And NormalizedElementOfMagmaRingModuloRelations is a misleading name.)

@fingolfin fingolfin Jun 8, 2026

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I wish I had made a note what the error was / why this change is the correct fix sigh

@ThomasBreuer ThomasBreuer Jun 9, 2026

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NormalizedElementOfMagmaRingModuloRelations is called in the GAP library only in lib/mgmring.gi. In all cases, Objectify is called immediately afterwards with the result. For the old code, this means that the object had already the desired type before the Objectify call, and gets objectified again with the same type.

In this sense, I think the library code does not produce wrong results. Nevertheless, the old code contradicts the definition of NormalizedElementOfMagmaRingModuloRelations. And there may be code outside lib/mgmring.gi which wants to use NormalizedElementOfMagmaRingModuloRelations. If the package tests do not show an example where the proposed change yields a different result then we should just apply the proposed fix and add a test, perhaps even as a manual example.

gap> R:= GroupRing( Rationals, SymmetricGroup( 3 ) );;
gap> Fam:= FamilyObj( Zero( R ) );;
gap> x:= Sum( GeneratorsOfAlgebra( R ) );;
gap> descr:= [ 0, CoefficientsAndMagmaElements( x ) ];;
gap> NormalizedElementOfMagmaRingModuloRelations( Fam, descr ) = descr;
true
gap> R:= FreeLieAlgebra( Rationals, 2 );;
gap> Fam:= FamilyObj( Zero( R ) );;
gap> x:= Sum( GeneratorsOfAlgebra( R ) );;
gap> descr:= [ 0, CoefficientsAndMagmaElements( x ) ];;
gap> NormalizedElementOfMagmaRingModuloRelations( Fam, descr ) = descr;
true

(The first true comes from a correct NormalizedElementOfMagmaRingModuloRelations method, the second true will occur only after the fix.)


end );

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29 changes: 18 additions & 11 deletions lib/type1.g
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Expand Up @@ -569,13 +569,6 @@ BIND_GLOBAL( "FlagsObj", obj -> FlagsType( TypeObj( obj ) ) );
BIND_GLOBAL( "DataObj", obj -> DataType( TypeObj( obj ) ) );


BIND_GLOBAL( "IsNonAtomicComponentObjectRepFlags",
FLAGS_FILTER(IsNonAtomicComponentObjectRep));
BIND_GLOBAL( "IsAtomicPositionalObjectRepFlags",
FLAGS_FILTER(IsAtomicPositionalObjectRep));
BIND_GLOBAL( "IsReadOnlyPositionalObjectRepFlags",
FLAGS_FILTER(IsReadOnlyPositionalObjectRep));

#############################################################################
##
#F Objectify( <type>, <obj> )
Expand All @@ -592,26 +585,40 @@ BIND_GLOBAL( "Objectify", function ( type, obj )
if not IsType( type ) then
Error("<type> must be a type");
fi;
flags := FlagsType(type);
if IsHPCGAP then
flags := FlagsType(type);
if IS_LIST( obj ) then
if IS_SUBSET_FLAGS(flags, IsAtomicPositionalObjectRepFlags) then
if IS_SUBSET_FLAGS(flags, FLAGS_FILTER(IsAtomicPositionalObjectRep)) then
FORCE_SWITCH_OBJ( obj, FixedAtomicList(obj) );
fi;
elif IS_REC( obj ) then
if IS_ATOMIC_RECORD(obj) then
if IS_SUBSET_FLAGS(flags, IsNonAtomicComponentObjectRepFlags) then
if IS_SUBSET_FLAGS(flags, FLAGS_FILTER(IsNonAtomicComponentObjectRep)) then
FORCE_SWITCH_OBJ( obj, FromAtomicRecord(obj) );
fi;
elif not IS_SUBSET_FLAGS(flags, IsNonAtomicComponentObjectRepFlags) then
elif not IS_SUBSET_FLAGS(flags, FLAGS_FILTER(IsNonAtomicComponentObjectRep)) then
FORCE_SWITCH_OBJ( obj, AtomicRecord(obj) );
fi;
fi;
fi;
if IS_LIST( obj ) then
#Assert(0, IS_SUBSET_FLAGS(flags, FLAGS_FILTER(IsPositionalObjectRep)));
Assert(0, not IS_SUBSET_FLAGS(flags, FLAGS_FILTER(IsComponentObjectRep)));
Comment on lines +605 to +606

@fingolfin fingolfin Oct 25, 2024

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Maybe disable this by default, but have it enabled e.g. in most test suites (as long as the use START_TEST)?

Suggested change
#Assert(0, IS_SUBSET_FLAGS(flags, FLAGS_FILTER(IsPositionalObjectRep)));
Assert(0, not IS_SUBSET_FLAGS(flags, FLAGS_FILTER(IsComponentObjectRep)));
#Assert(1, IS_SUBSET_FLAGS(flags, FLAGS_FILTER(IsPositionalObjectRep)));
Assert(1, not IS_SUBSET_FLAGS(flags, FLAGS_FILTER(IsComponentObjectRep)));

if not IS_SUBSET_FLAGS(flags, FLAGS_FILTER(IsPositionalObjectRep)) then
INFO_DEBUG(1, "Objectify: type does not imply IsPositionalObjectRep ",
INPUT_FILENAME(), ":", STRING_INT(INPUT_LINENUMBER()));
fi;
SET_TYPE_POSOBJ( obj, type );
elif IS_REC( obj ) then
#Assert(0, IS_SUBSET_FLAGS(flags, FLAGS_FILTER(IsComponentObjectRep)));
Assert(0, not IS_SUBSET_FLAGS(flags, FLAGS_FILTER(IsPositionalObjectRep)));
Comment on lines +613 to +614

@fingolfin fingolfin Oct 25, 2024

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Suggested change
#Assert(0, IS_SUBSET_FLAGS(flags, FLAGS_FILTER(IsComponentObjectRep)));
Assert(0, not IS_SUBSET_FLAGS(flags, FLAGS_FILTER(IsPositionalObjectRep)));
#Assert(1, IS_SUBSET_FLAGS(flags, FLAGS_FILTER(IsComponentObjectRep)));
Assert(1, not IS_SUBSET_FLAGS(flags, FLAGS_FILTER(IsPositionalObjectRep)));

if not IS_SUBSET_FLAGS(flags, FLAGS_FILTER(IsComponentObjectRep)) then
INFO_DEBUG(1, "Objectify: type does not imply IsComponentObjectRep ",
INPUT_FILENAME(), ":", STRING_INT(INPUT_LINENUMBER()));
fi;
SET_TYPE_COMOBJ( obj, type );
else
Error("<obj> must be a list or a record");
fi;
if not ( IGNORE_IMMEDIATE_METHODS
or IsNoImmediateMethodsObject(obj) ) then
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2 changes: 1 addition & 1 deletion tst/testinstall/kernel/gap.tst
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Expand Up @@ -7,7 +7,7 @@ gap> START_TEST("kernel/gap.tst");
# in ViewObj; afterwards everything should still work as before
gap> l := [ ~ ];; r := rec(a:=~);;
gap> cat := NewCategory("IsMockObject", IsObject);;
gap> type := NewType(NewFamily("MockFamily"), cat);;
gap> type := NewType(NewFamily("MockFamily"), cat and IsPositionalObjectRep);;
gap> InstallMethod(ViewObj, [cat], function(s) Error("oops"); end);
gap> InstallMethod(PrintObj, [cat], function(s) Error("uups"); end);
gap> x:=Objectify(type,[]); r; Print(l, "\n");
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4 changes: 2 additions & 2 deletions tst/testinstall/kernel/opers.tst
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Expand Up @@ -294,7 +294,7 @@ gap> CLEAR_CACHE_INFO();
gap> opcheck := OPERS_CACHE_INFO();;
#@if GAPInfo.KernelInfo.KernelDebug and IsHPCGAP
gap> opcheck{[1..11]};
[ 2, 0, 0, 6, 0, 0, 6, 0, 0, 2, 0 ]
[ 2, 0, 0, 6, 0, 0, 10, 0, 0, 2, 0 ]
#@fi

# FIXME: the following code skips entry 4 (OperationHit, which is normally
Expand Down Expand Up @@ -338,7 +338,7 @@ gap> opcheck{[1..11]};
#
#@if GAPInfo.KernelInfo.KernelDebug and not IsHPCGAP
gap> opcheck{Difference([1..11], [4])};
[ 2, 0, 0, 0, 0, 4, 0, 0, 2, 0 ]
[ 2, 0, 0, 0, 0, 8, 0, 0, 2, 0 ]
#@fi
#@if not GAPInfo.KernelInfo.KernelDebug
gap> opcheck{[1..11]};
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2 changes: 1 addition & 1 deletion tst/testinstall/object.tst
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Expand Up @@ -4,7 +4,7 @@
gap> START_TEST("object.tst");

# test some standard object types
gap> r := Objectify(TYPE_KERNEL_OBJECT, rec());
gap> r := [];; SET_TYPE_DATOBJ(r,TYPE_KERNEL_OBJECT);
<kernel object>
gap> KnownAttributesOfObject(r);
[ ]
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