Re: problems using classwide types

[je@bton.ac.uk (John English)]

andy billimore (billimad@dcs.gla.NOSPAM.ac.uk) wrote:
:   type Transaction_Type is tagged private;
:   type Transaction_Ptr_Type is access all Transaction_Type'Class;
:   type Check_Type is new Transaction_Type with private;

: The main program looks like this -

: with Transactions; use Transactions;
: with Transactions.Checks; use Transactions.Checks;
: procedure Main is
:    L_Check : Check_Type;

L_Check : aliased Check_Type; -- so you can get an access value to it

:    TP : Transaction_Ptr_Type;
: begin
:    TP := new Check_Type;
:    TP := L_Check; -- Error (see below)

-- the value assigned to TP must be of type Transaction_Ptr_Type
-- L_Check is a Check_Type, not a Transaction_Ptr_Type, so do this:
TP := L_Check'Access;  -- i.e. a "pointer" to L_Check

: end Main;

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 John English              | mailto:je@brighton.ac.uk
 Senior Lecturer           | http://www.comp.it.bton.ac.uk/je
 Dept. of Computing        | fax: (+44) 1273 642405
 University of Brighton    |
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