DynamicBitset

• User documentation
  • Examples
  • Constructors
  • Functions
  • Member functions
  • output options
• Maintainer documentation
• Bugs, shortcomings and other ideas
  • boost?
  • Stretchable?
• Main changes

User documentation

Class for representing square free monomials, or subsets of integers.

Similar to a C++ bitset except that its size does not need to be fixed at compile time (hence the adjective dynamic).

Examples

• ex-DynamicBitset1.C

Constructors

• DynamicBitset(long n=0)
• DynamicBitset(ConstRefPPMonoidElem pp)
• DynamicBitset(const DynamicBitset&)

Functions

• unsigned long size(const DynamicBitset& b) { return b.mySize(); }
• std::ostream& operator<<(std::ostream&, const DynamicBitset&);

With sanity checks:

• DynamicBitset operator|(const DynamicBitset&, const DynamicBitset&); -- bitwise or
• DynamicBitset operator&(const DynamicBitset&, const DynamicBitset&); -- bitwise and
• DynamicBitset operator-(const DynamicBitset&, const DynamicBitset&); -- bitwise diff
• DynamicBitset operator^(const DynamicBitset&, const DynamicBitset&); -- bitwise xor
• bool IsSubset(const DynamicBitset&, const DynamicBitset&);
• bool IsDisjoint(const DynamicBitset&, const DynamicBitset&);
• bool Is1At(const DynamicBitset&, std::size_t index);
• PPMonoidElem NewPP(const PPMonoid&, const DynamicBitset&);

Member functions

• unsigned int mySize() const; -- number of bits
• bool IamAll0s() const; -- *this = [00000...0000]
• bool IamAll1s() const; -- *this = [11111...1111]

Without sanity checks:

• DynamicBitset& mySet(std::size_t index, bool val); -- *this[index] = val
• DynamicBitset& mySet(std::size_t index); -- *this[index] = true``

• DynamicBitset& operator=(const DynamicBitset& rhs);
• DynamicBitset& operator&=(const DynamicBitset& rhs); -- and
• DynamicBitset& operator|=(const DynamicBitset& rhs); -- or
• DynamicBitset& operator^=(const DynamicBitset& rhs); -- xor
• DynamicBitset& operator-=(const DynamicBitset& rhs); -- diff

• bool Iam1At(std::size_t index) const; -- *this[index] == 1
• bool operator<(const DynamicBitset& rhs) const; -- wrt Xel
• bool IamSubset(const DynamicBitset& rhs) const; -- subset of rhs
• bool IamDisjoint(const DynamicBitset& rhs) const;

• bool operator==(const DynamicBitset& rhs) const {return myVec==rhs.myVec;}
• bool operator!=(const DynamicBitset& rhs) const {return myVec!=rhs.myVec;}

output options

Default printing style is clean, i.e. as an STL bitset of the same size. Printing style can be changed by setting the variable DynamicBitset::ourOutputStyle (see ex-DynamicBitset1.C).

Member functions

• void myOutputSelf(std::ostream& out) const; -- as a bitset of same size
• void myOutputSelf8(std::ostream& out) const; -- blocks of 8/ourNumBitsInBlock, for readability
• void myOutputSelfLong(std::ostream& out) const; -- as reversed vector<unsigned long>

Maintainer documentation

Member fields (private)

The size_t constant DynamicBitset::ourNumBitsInBlock stores number of bits of an unsigned long (normally 32 or 64).

So a DynamicBitset stores a STL vector of STL bitsets of (constant) size ourNumBitsInBlock called myVec. The field mySizeValue is the number of bits we intend to use. (e.g. in a 32 bit machine a DynamicBitset of size 60 is stored as a vector with 2 BitBlocks and will have 4 unused bits)

     enum OutputStyle {clean, AsRevVecOfLong, WithSeparators};

Member functions (private)

• void myResize(std::size_t n); -- only for ctors
• unsigned int myVecSize() const; -- number of BitBlocks in vector

Bugs, shortcomings and other ideas

boost?

This class is needed because C++ bitset length has to be fixed at compile time. There is a class in boost named dynamic_bitset: if/when we decide CoCoALib inlude boost DynamicBitset will just call the boost implementation.

Stretchable?

DynamicBitsets, unlike boost's dynamic_bitsets, are not stretchable: the resize function is private. They are used to represent square-free power-products, therefore changing size does not make sense. But there is no technical reason to forbid it, so we might make it available.

Main changes

2010

• moved definition of class facet from "TmpIsTree`` into DynamicBitset.H,C (and renamed). Rearranged and changed names for similarity with bitsets in STL and boost. Stuctured in safe or fast functions according to coding conventions. Test and example.