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Implement find_first(pos).
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@Siapran @jeking3
Siapran authored and jeking3 committed Nov 26, 2024
1 parent b33c19e commit 34f55c7
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Showing 4 changed files with 51 additions and 37 deletions.
10 changes: 10 additions & 0 deletions dynamic_bitset.html
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Expand Up @@ -238,6 +238,7 @@ <h3><a id ="synopsis">Synopsis</a></h3>
bool <a href="#intersects">intersects</a>(const dynamic_bitset&amp; a) const;

size_type <a href="#find_first">find_first</a>() const;
size_type <a href="#find_first_off">find_first</a>(size_type pos) const;
size_type <a href="#find_next">find_next</a>(size_type pos) const;

};
Expand Down Expand Up @@ -1373,6 +1374,15 @@ <h3><a id="member-functions">Member Functions</a></h3>
<b>Returns:</b> the lowest index <tt>i</tt> such as bit <tt>i</tt>
is set, or <tt>npos</tt> if <tt>*this</tt> has no on bits.

<hr />
<pre>
size_type <a id = "find_first_off">find_first</a>(size_type pos) const;
</pre>

<b>Returns:</b> the lowest index <tt>i</tt> greater or equal to
<tt>offset</tt> such as bit <tt>i</tt> is set, or <tt>npos</tt> if
no such index exists.

<hr />
<pre>
size_type <a id="find_next">find_next</a>(size_type pos) const;
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20 changes: 12 additions & 8 deletions include/boost/dynamic_bitset/dynamic_bitset.hpp
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Expand Up @@ -325,6 +325,7 @@ class dynamic_bitset

// lookup
size_type find_first() const;
size_type find_first(size_type pos) const;
size_type find_next(size_type pos) const;


Expand Down Expand Up @@ -1326,7 +1327,7 @@ to_ulong() const

// Check for overflows. This may be a performance burden on very
// large bitsets but is required by the specification, sorry
if (find_next(ulong_width - 1) != npos)
if (find_first(ulong_width) != npos)
BOOST_THROW_EXCEPTION(std::overflow_error("boost::dynamic_bitset::to_ulong overflow"));


Expand Down Expand Up @@ -1486,17 +1487,12 @@ dynamic_bitset<Block, Allocator>::find_first() const
return m_do_find_from(0);
}


template <typename Block, typename Allocator>
typename dynamic_bitset<Block, Allocator>::size_type
dynamic_bitset<Block, Allocator>::find_next(size_type pos) const
dynamic_bitset<Block, Allocator>::find_first(size_type pos) const
{

const size_type sz = size();
if (pos >= (sz-1) || sz == 0)
return npos;

++pos;
if (pos >= sz) return npos;

const size_type blk = block_index(pos);
const block_width_type ind = bit_index(pos);
Expand All @@ -1508,7 +1504,15 @@ dynamic_bitset<Block, Allocator>::find_next(size_type pos) const
pos + static_cast<size_type>(detail::lowest_bit(fore))
:
m_do_find_from(blk + 1);
}


template <typename Block, typename Allocator>
typename dynamic_bitset<Block, Allocator>::size_type
dynamic_bitset<Block, Allocator>::find_next(size_type pos) const
{
if (pos == npos) return npos;
return find_first(pos + 1);
}


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28 changes: 14 additions & 14 deletions test/bitset_test.hpp
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Expand Up @@ -967,25 +967,25 @@ struct bitset_test {
BOOST_TEST(b.intersects(a) == have_intersection);
}

static void find_first(const Bitset& b)
static void find_first(const Bitset& b, typename Bitset::size_type offset = 0)
{
// find first non-null bit, if any
typename Bitset::size_type i = 0;
while (i < b.size() && b[i] == 0)
++i;

if (i == b.size())
BOOST_TEST(b.find_first() == Bitset::npos); // not found;
else {
BOOST_TEST(b.find_first() == i);
BOOST_TEST(b.test(i) == true);
}
// find first non-null bit from offset onwards, if any
typename Bitset::size_type i = offset;
while (i < b.size() && b[i] == 0)
++i;

if (i >= b.size())
BOOST_TEST(b.find_first(offset) == Bitset::npos); // not found;
else {
BOOST_TEST(b.find_first(offset) == i);
BOOST_TEST(b.test(i) == true);
}
}

static void find_next(const Bitset& b, typename Bitset::size_type prev)
static void find_pos(const Bitset& b, typename Bitset::size_type pos)
{
BOOST_TEST(next_bit_on(b, prev) == b.find_next(prev));
find_first(b, pos);
BOOST_TEST(next_bit_on(b, pos) == b.find_next(pos));
}

static void operator_equal(const Bitset& a, const Bitset& b)
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30 changes: 15 additions & 15 deletions test/dyn_bitset_unit_tests3.cpp
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Expand Up @@ -329,26 +329,26 @@ void run_test_cases( BOOST_EXPLICIT_TEMPLATE_TYPE(Block) )
Tests::find_first(b);
}
//=====================================================================
// Test find_next
// Test find_next and offset find_first
{
// empty bitset
bitset_type b;

// check
Tests::find_next(b, 0);
Tests::find_next(b, 1);
Tests::find_next(b, 200);
Tests::find_next(b, b.npos);
Tests::find_pos(b, 0);
Tests::find_pos(b, 1);
Tests::find_pos(b, 200);
Tests::find_pos(b, b.npos);
}
{
// bitset of size 1 (find_next can never find)
bitset_type b(1, 1ul);

// check
Tests::find_next(b, 0);
Tests::find_next(b, 1);
Tests::find_next(b, 200);
Tests::find_next(b, b.npos);
Tests::find_pos(b, 0);
Tests::find_pos(b, 1);
Tests::find_pos(b, 200);
Tests::find_pos(b, b.npos);
}
{
// all-1s bitset
Expand All @@ -358,9 +358,9 @@ void run_test_cases( BOOST_EXPLICIT_TEMPLATE_TYPE(Block) )
// check
const typename bitset_type::size_type larger_than_size = 5 + b.size();
for(typename bitset_type::size_type i = 0; i <= larger_than_size; ++i) {
Tests::find_next(b, i);
Tests::find_pos(b, i);
}
Tests::find_next(b, b.npos);
Tests::find_pos(b, b.npos);
}
{
// a bitset with 1s at block boundary only
Expand All @@ -379,9 +379,9 @@ void run_test_cases( BOOST_EXPLICIT_TEMPLATE_TYPE(Block) )
// check
const typename bitset_type::size_type larger_than_size = 5 + b.size();
for (i = 0; i <= larger_than_size; ++i) {
Tests::find_next(b, i);
Tests::find_pos(b, i);
}
Tests::find_next(b, b.npos);
Tests::find_pos(b, b.npos);

}
{
Expand All @@ -397,9 +397,9 @@ void run_test_cases( BOOST_EXPLICIT_TEMPLATE_TYPE(Block) )
// check
const typename bitset_type::size_type larger_than_size = 5 + b.size();
for (i = 0; i <= larger_than_size; ++i) {
Tests::find_next(b, i);
Tests::find_pos(b, i);
}
Tests::find_next(b, b.npos);
Tests::find_pos(b, b.npos);

}
//=====================================================================
Expand Down

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