PTypes: cset: operators

#include <ptypes.h>

class cset {
    // assignment
    cset& operator =(const cset& s);

    // union
    cset& operator +=(const cset& s);
    cset& operator +=(char b);
    cset  operator +(const cset& s) const;
    cset  operator +(char b) const;
    friend cset operator +(char b, const cset& s);

    // difference
    cset& operator -=(const cset& s);
    cset& operator -=(char b);
    cset  operator -(const cset& s) const;
    cset  operator -(char b) const;

    // intersection
    cset& operator *=(const cset& s);
    cset  operator *(const cset& s) const;

    // comparison
    bool operator ==(const cset& s) const;
    bool operator !=(const cset& s) const;
    bool operator <=(const cset& s) const;
    bool operator >=(const cset& s) const;

    // membership
    friend bool operator& (char b, const cset& s);
}

The following rules apply to +, -, and *:

An ordinal O is in X + Y if and only if O is in X or Y (or both). Equivalent of bitwise OR.
O is in X - Y if and only if O is in X but not in Y. Equivalent of bitwise AND NOT.
O is in X * Y if and only if O is in both X and Y. Equivalent of bitwise AND.

The following rules apply to comparison operations <=, >=, ==, !=:

X <= Y is true just in case every member of X is a member of Y; Z >= W is equivalent to W <= Z.
U == V is true just in case U and V contain exactly the same members; otherwise, U != V is true.

For an ordinal O and a set S, O & S is true just in case O is a member of S. Unlike the Pascal language, where membership operator is in, PTypes uses ampersand "&" as a membership test operator.

Note: regardless of whether default char is signed or unsigned (usually set through compiler options) cset always treats char arguments as unsigned. This means, if the value of an argument is -1, e.g. in call to operator & or operator +, the value will be converted to 255, -2 will be treated as 254, etc.