Goose  Artifact [91ed82a910]

Artifact 91ed82a910d9802dbead323e79a89201016ccd1a69e867af21d52c084c944e76:

• File bs/sema/uni-context.h — part of check-in [ce11e48c1b] at 2019-01-03 13:43:26 on branch trunk — First draft implementation of hole vs hole unification. (user: achavasse size: 1965)

#ifndef EMPATHY_SEMA_UNI_CONTEXT_H
#define EMPATHY_SEMA_UNI_CONTEXT_H

namespace empathy::sema
{
    class UnificationRuleSet;

    class UnificationContext
    {
        public:
            static constexpr uint32_t InvalidIndex = numeric_limits< uint32_t >::max();

            UnificationContext( const ptr< UnificationRuleSet >& rules );
            UnificationContext( ptr< UnificationRuleSet >&& rules );

            const auto& rules() const { return m_rules; }

            uint32_t getLHSHoleIndex( const StringId& name ) const;
            uint32_t getRHSHoleIndex( const StringId& name ) const;

            uint32_t createValue();
            void setLHSHoleIndex( const StringId& name, uint32_t index );
            void setRHSHoleIndex( const StringId& name, uint32_t index );

            const optional< Term >& getValue( uint32_t index ) const
            {
                assert( m_values.size() > index );
                return m_values[index];
            }

            void setValue( uint32_t index, Term&& val )
            {
                assert( m_values.size() > index );
                m_values = m_values.set( index, move( val ) );
            }

            UnificationContext& flip()
            {
                swap( m_currentLHSNamespaceIndex, m_currentRHSNamespaceIndex );
                return *this;
            }

        private:
            ptr< UnificationRuleSet >                   m_rules;
            immer::vector< optional< Term > >           m_values;

            uint32_t                                    m_currentLHSNamespaceIndex = 1;
            uint32_t                                    m_currentRHSNamespaceIndex = 2;

            using HoleName = pair< StringId, uint32_t >;

            struct cow
            {
                unordered_map< HoleName, uint32_t >     m_holes;
            };

            ptr< cow >                                  m_pCoW = make_shared< cow >();
    };
}

#endif