source: libcfa/src/bits/stack.hfa@ b66d14a

#pragma once

#include "bits/collection.hfa"

// A Stack(T) is a Collection(T) defining the ordering that nodes are returned by drop() in the reverse order from those
// added by add(). T must be a public descendant of uColable.

// The implementation is a typical singly-linked list, except the next field of the last element points to itself
// instead of being null.

forall( dtype T | { T *& Next ( T * ); } ) {
        struct Stack {
                inline Collection;                                                              // Plan 9 inheritance
        };

        inline {
                // wrappers to make Collection have T
                T & head( Stack(T) & s ) with( s ) {
                        return *(T *)head( (Collection &)s );
                } // post: empty() & head() == 0 | !empty() & head() in *this

                void ?{}( Stack(T) &, const Stack(T) & ) = void; // no copy
                Stack(T) & ?=?( const Stack(T) & ) = void;              // no assignment

                void ?{}( Stack(T) & s ) with( s ) {
                        ((Collection &)s){};
                } // post: empty()

                T & top( Stack(T) & s ) with( s ) {
                        return head( s );
                }

                T & addHead( Stack(T) & s, T & n ) with( s ) {
                        #ifdef __CFA_DEBUG__
                        if ( listed( (Colable &)(n) ) ) abort( "(Stack &)%p.addHead( %p ) : Node is already on another list.", &s, n );
                        #endif // __CFA_DEBUG__
                        Next( &n ) = &head( s ) ? &head( s ) : &n;
                        root = &n;
                        return n;
                }

                T & add( Stack(T) & s, T & n ) with( s ) {
                        return addHead( s, n );
                }

                T & push( Stack(T) & s, T & n ) with( s ) {
                        return addHead( s, n );
                }

                T & drop( Stack(T) & s ) with( s ) {
                        T & t = head( s );
                        if ( root ) {
                                root = ( T *)Next( (T *)root );
                                if ( &head( s ) == &t ) root = 0p;              // only one element ?
                                Next( &t ) = 0p;
                        } // if
                        return t;
                }

                T & pop( Stack(T) & s ) with( s ) {
                        return drop( s );
                }
        } // distribution
} // distribution

// A StackIter(T) is a subclass of ColIter(T) that generates the elements of a Stack(T).  It returns the elements in the
// order returned by drop().

forall( dtype T | { T *& Next ( T * ); } ) {
        struct StackIter {
                inline ColIter;                                                                 // Plan 9 inheritance
        };      

        inline {
                void ?{}( StackIter(T) & si ) with( si ) {
                        ((ColIter &)si){};
                } // post: curr == 0p

                // create an iterator active in stack s
                void ?{}( StackIter(T) & si, Stack(T) & s ) with( si ) {
                        curr = &head( s );
                } // post: curr = {e in s}

                void ?{}( StackIter(T) & si, T & start ) with( si ) {
                        curr = &start;
                } // post: curr = {e in s}

                // make existing iterator active in stack s
                void over( StackIter(T) & si, Stack(T) & s ) with( si ) {
                        curr = &head( s );
                } // post: curr = {e in s}

                bool ?|?( StackIter(T) & si, T && tp ) with( si ) {
                        if ( curr ) {
                                &tp = Curr( si );
                                T * n = Next( Curr( si ) );
                                curr = n == Curr( si ) ? 0p : n;
                        } else &tp = 0p;
                        return &tp != 0p;
                }
        } // distribution
} // distribution