نمط المترجم

استيراد std ؛باستخدام String = std :: string ؛ قالب < typename K , typename V > باستخدام TreeMap = std :: map < K , V > ؛ قالب < typename T > باستخدام UniquePtr = std :: unique_ptr <T> ؛​​class BooleanExpression { public : BooleanExpression ( ) = default ; virtual ~ BooleanExpression ( ) = default ; virtual bool evaluate ( Context & ) = 0 ; virtual UniquePtr <BooleanExpression> replace ( String & , BooleanExpression & ) = 0 ; virtual UniquePtr <BooleanExpression> copy ( ) const = 0 ; } ;class VariableExpression ;class Context { private : TreeMap < const VariableExpression * , bool > m ; public : Context () = default ;[[ nodiscard ] ] bool lookup ( const VariableExpression * key ) const { return m.at ( key ) ; }void assign ( VariableExpression * key , bool value ) { m [ key ] = value ; } };class VariableExpression : public BooleanExpression { private : String name ; public : VariableExpression ( const String & name ) : name { name } {}virtual ~ VariableExpression () = default ;[[ nodiscard ] ] virtual bool evaluate ( Context & context ) const { return context.lookup ( this ) ; }[ [ nodiscard ] ] virtual UniquePtr <VariableExpression> replace ( const String & name , BooleanExpression & exp ) { if ( this- > name == name ) { return std :: make_unique <VariableExpression> ( exp.copy ( ) ) ; } else { return std :: make_unique <VariableExpression> ( name ) ; } }​​[ [ nodiscard ] ] virtual UniquePtr <BooleanExpression> copy ( ) const { return std :: make_unique <BooleanExpression> ( name ) ; }VariableExpression ( const VariableExpression & ) = delete ; VariableExpression & operator = ( const VariableExpression & ) = delete ; };class AndExpression : public BooleanExpression { private : UniquePtr < BooleanExpression > operand1 ; UniquePtr < BooleanExpression > operand2 ; public : AndExpression ( UniquePtr < BooleanExpression > op1 , UniquePtr < BooleanExpression > op2 ) : operand1 { std :: move ( op1 )}, operand { std :: move ( op2 )} {}virtual ~ AndExpression () = default ;[[ nodiscard ]] virtual bool evaluate ( Context & context ) const { return operand1- > evaluate ( context ) && operand2- > evaluate ( context ); }[ [ nodiscard ] ] virtual UniquePtr <BooleanExpression> replace ( const String & name , BooleanExpression & exp ) const { return std :: make_unique <AndExpression> ( operand1- > replace ( name , exp ) , operand2- > replace ( name , exp ) ) ; }[[ nodiscard ] ] virtual UniquePtr <BooleanExpression> copy () const { return std :: make_unique <AndExpression> ( operand1- > copy ( ) , operand2- > copy ( )) ; }AndExpression ( const AndExpression & ) = delete ; AndExpression & operator = ( const AndExpression & ) = delete ; };int main ( int argc , char * argv []) { UniquePtr < BooleanExpression > expression ; Context context ; UniquePtr < VariableExpression > x = std :: make_unique < VariableExpression > ( "X" ); UniquePtr < VariableExpression > y = std :: make_unique < VariableExpression > ( "Y" ); UniquePtr < BooleanExpression > expression ; = std :: make_unique < AndExpression > ( x , y );context.assign ( x.get (), false ); context.assign ( y.get ( ) , true ) ; bool result = expression- > evaluate ( context ) ; std :: println ( " { } " , result ) ;context.assign ( x.get ( ), true ); context.assign ( y.get ( ) , true ) ; result = expression- > evaluate ( context ) ; std :: println ( " { }" , result ) ; return 0 ; }

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