PTypes: cset: operators

Top: Basic types: 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.

See also: Constructors, Manipulation

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