GLOBAL
    DECLARE Alive : INTEGER
ENDGLOBAL
CLASS Box
    Value : INTEGER
    OVERLOAD PROCEDURE NEW()
        Alive <- Alive + 1
    ENDPROCEDURE
    OVERLOAD IMPLICIT PROCEDURE NEW(Number : INTEGER)
        Value <- Number
        Alive <- Alive + 1
    ENDPROCEDURE
    OVERLOAD PROCEDURE NEW(BYREF Other : Box)
        Value <- Other.Value
        Alive <- Alive + 1
    ENDPROCEDURE
    PROCEDURE DELETE()
        Alive <- Alive - 1
    ENDPROCEDURE
ENDCLASS
FUNCTION Read(Value : Box) RETURNS INTEGER
    RETURN Value.Value
ENDFUNCTION
OVERLOAD FUNCTION Pick(Value : Box) RETURNS INTEGER
    RETURN 100 + Value.Value
ENDFUNCTION
OVERLOAD FUNCTION Pick(Value : INTEGER) RETURNS INTEGER
    RETURN 200 + Value
ENDFUNCTION
OVERLOAD FUNCTION Only(Value : Box) RETURNS INTEGER
    RETURN Value.Value
ENDFUNCTION
OVERLOAD FUNCTION OPERATOR+(A : Box, B : Box) RETURNS INTEGER
    RETURN A.Value + B.Value
ENDFUNCTION
OVERLOAD FUNCTION OPERATOR=(A : Box, B : Box) RETURNS BOOLEAN
    RETURN A.Value = B.Value
ENDFUNCTION
FUNCTION Make() RETURNS Box
    RETURN 9
ENDFUNCTION
PROCEDURE Exercise()
    DECLARE B : Box
    B <- 7
    OUTPUT B.Value, ":", Read(8), ":", Pick(1), ":", Only(6), ":", B + 2
    OUTPUT Read(Make())
    CASE OF B
        7 : OUTPUT TRUE
        OTHERWISE : OUTPUT FALSE
    ENDCASE
ENDPROCEDURE
FUNCTION Fail() RETURNS INTEGER
    THROW
ENDFUNCTION
PROCEDURE Pair(Value : Box, Number : INTEGER)
ENDPROCEDURE
CALL Exercise()
OUTPUT Alive
TRY
    CALL Pair(1, Fail())
CATCH
    OUTPUT Alive
ENDTRY