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Fix a bug where calling NextIterator on a "done" list iterator caused it to seemingly switch back to "not done" status #4232

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merged 4 commits into from
Jan 27, 2021
Merged

Fix a bug where calling NextIterator on a "done" list iterator caused it to seemingly switch back to "not done" status #4232

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c619dc6
list.gi: tweak IsDoneIterator_List
wilfwilson Jan 27, 2021
c6485f7
list.gi: speed up NextIterator_[Dense]List
wilfwilson Jan 27, 2021
49a97bd
list.gi: restructure IteratorList
wilfwilson Jan 27, 2021
a4784cb
Remove commented-out IsDoneIterator_DenseList
wilfwilson Jan 27, 2021
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31 changes: 17 additions & 14 deletions lib/list.gi
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Original file line number Diff line number Diff line change
Expand Up @@ -739,28 +739,32 @@ InstallMethod( SSortedList,
## lists.)
##
BindGlobal( "IsDoneIterator_List",
iter -> ( iter!.pos = iter!.len ) );
iter -> ( iter!.pos >= iter!.len ) );

BindGlobal( "NextIterator_List", function ( iter )
if iter!.pos = Length( iter!.list ) then
local p, l;
p := iter!.pos;
if p = iter!.len then
Error("<iter> is exhausted");
fi;
iter!.pos := iter!.pos + 1;
while not IsBound( iter!.list[ iter!.pos ] ) do
iter!.pos := iter!.pos + 1;
l := iter!.list;
p := p + 1;
while not IsBound( l[ p ] ) do
p := p + 1;
od;
return iter!.list[ iter!.pos ];
iter!.pos := p;
return l[ p ];
end );

#BindGlobal( "IsDoneIterator_DenseList",
# iter -> not IsBound( iter!.list[ iter!.pos + 1 ] ) );

BindGlobal( "NextIterator_DenseList", function ( iter )
iter!.pos := iter!.pos + 1;
local p;
p := iter!.pos + 1;
iter!.pos := p;
#if not IsBound( iter!.list[ iter!.pos ] ) then
# Error("<iter> is exhausted");
#fi;
return iter!.list[ iter!.pos ];
return iter!.list[ p ];
end );

BindGlobal( "ShallowCopy_List",
Expand All @@ -776,14 +780,13 @@ InstallGlobalFunction( IteratorList, function ( list )
#T call `Immutable'?
pos := 0,
len := Length(list),
IsDoneIterator := IsDoneIterator_List,
ShallowCopy := ShallowCopy_List );

if IsDenseList( list ) and not IsMutable( list ) then
iter.IsDoneIterator := IsDoneIterator_List;
iter.NextIterator := NextIterator_DenseList;
iter.NextIterator := NextIterator_DenseList;
else
iter.IsDoneIterator := IsDoneIterator_List;
iter.NextIterator := NextIterator_List;
iter.NextIterator := NextIterator_List;
fi;

return IteratorByFunctions( iter );
Expand Down
56 changes: 56 additions & 0 deletions tst/testinstall/list.tst
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Original file line number Diff line number Diff line change
Expand Up @@ -554,5 +554,61 @@ gap> MakeImmutable(l);;
gap> IsIdenticalObj(AsSet(l), l);
true

# IteratorList
# immutable dense list
gap> tmp := MakeImmutable([1, 2, 3, 4]);
[ 1, 2, 3, 4 ]
gap> it := IteratorList(tmp);
<iterator>
gap> for x in it do Print(x); od; Print("\n");
1234
gap> IsDoneIterator(it);
true
gap> NextIterator(it);
Error, List Element: <list>[5] must have an assigned value
gap> IsDoneIterator(it);
true

# mutable dense list
gap> tmp := [1 .. 4];;
gap> it := IteratorList(tmp);
<iterator>
gap> for x in it do Print(x); od; Print("\n");
1234
gap> IsDoneIterator(it);
true
gap> NextIterator(it);
Error, <iter> is exhausted
gap> IsDoneIterator(it);
true

# immutable non-dense list
gap> tmp := MakeImmutable([, 2, 3, , 5, 6,]);
[ , 2, 3,, 5, 6 ]
gap> it := IteratorList(tmp);
<iterator>
gap> for x in it do Print(x); od; Print("\n");
2356
gap> IsDoneIterator(it);
true
gap> NextIterator(it);
Error, <iter> is exhausted
gap> IsDoneIterator(it);
true

# mutable non-dense list
gap> tmp := [, 2, 3, , 5, 6,];
[ , 2, 3,, 5, 6 ]
gap> it := IteratorList(tmp);
<iterator>
gap> for x in it do Print(x); od; Print("\n");
2356
gap> IsDoneIterator(it);
true
gap> NextIterator(it);
Error, <iter> is exhausted
gap> IsDoneIterator(it);
true

#
gap> STOP_TEST("list.tst");