Re: Help setting up an array of records

[Mark Johnson <mark_h_johnson@raytheon.com>]

Matt Thomas wrote:
> [help for homework]
> I'm using an array of records to represent the items in the vending machine
> but I dont know how to actually get the information into my array.  I need
> to specify the name of the item, its cost and the quantity left.
> 
> Here is the record and array declaration, any help would be grateful.
> 
> MACHINE_SLOTS  :   constant := 6; --
> 
> type PRODUCT_TYPE is
>    record
>          NAME      :   STRING (1..12);
>          LEN       :   POSITIVE;
>          PRICE     :   INTEGER;
>          QUANTITY  :   INTEGER;
>    end record;
> 
> type PRODUCT_TYPE_ARR is array (1..MACHINE_SLOTS) of PRODUCT_TYPE;
> 
> PRODUCT   :   PRODUCT_TYPE_ARR;

You didn't say much, so I can't judge what you know or don't know. You
also didn't say which text book you are using, so I'll make a couple
references to the ever so helpful Ada Reference Manual :-). [I don't
recommend reading the ARM unless you want to be a "language lawyer"
because it is not so easy to read...] You could look up the terms I
refer to in your text book to find the chapters where this is described.

 - 4.1 Names,
  o 4.1.1 - indexed components (into the array)
  o 4.1.3 - selected components (elements of the record)
  the methods described can be combined to refer to a single (or more
than one) component of the record within a single component (or slice)
in the array
 - 4.2 Literals, a specific value of the appropriate type
 - 4.3 Aggregates, 
  o 4.3.1 - record aggregates (for Product_Type)
  o 4.3.3 - array aggregates (for Product_Type_Arr)
  if you want to initialize several values at once (e.g., an "empty
product")
 - 5.2 Assignment statement, to replace the current value of a variable
with the result of an expression

There is a lot more than what I refer to that will likely confuse at
this point. For example, continue to use simple types until you
understand the rules of type conversion. Don't use slices unless you
clearly understand them as well. Do a simple example first and
generalize until you understand the basic rules.
  --Mark