Re: Unconstrained arrays

[cis.ohio-state.edu!math.ohio-state.edu!howland.reston.ans.net!darwin.sura .net!aplcen.apl.jhu.edu!ddsdx2.jhuapl.edu!dlc@ucbvax.Berkeley.EDU (Dave Collar d x7468)]

In <9308111528.aa04642@Paris.ics.uci.edu> kanderso@mabillon.ICS.UCI.EDU (Kennet
h Anderson) writes:

>Hello,

>  I have declared the following type (DynamicString is an imported type)

>        type Str_Array is array (Natural range <>) of DynamicString;

>Later when I try to declare objects of this type, the compiler likes this


>   Viewers : str_array(1 .. 6) := (Create("Airspeed_Guage"),
>                                   Create("Altimeter_Guage"),
>                                   Create("Compass_Guage"),
>                                   Create("Horizon_Guage"),
>                                   Create("ROC_Guage"),
>                                   Create("Turn_Guage"));

>but it does not like this

>   Viewers : str_array(1 .. 1) := (Create("text_artist"));

>Here is the error message generated by the SunAda 1.1 compiler


>--### A:error: RM 8.3: no visible identifier is of type str_array


>If I change the above declaration to

>   Viewers : str_array(1 .. 2) := (Create("text_artist"),
>                                   Create("ignore"));

>The compiler is happy again.

>  Can someone help me out on this?  Why can't I declare AND initialize
>an array of only one element?

You can.  the problem is that
  "Aggregates containing a single component association must always be
   given in named notation"  LRM 4.3(4)

  So change your declaration to either
 
    Viewers : str_array(1..1) := (1 => Create("text_artist")); 
    
        or
  
    Viewers : str_array(1..1) := (others => Create("text_artist")); 

  This rule is required so that the compiler can tell that it is an
  aggregate.  The compiler is not allowed to use any information from
  within the aggregate to determine the type of aggregate.  "An
  aggregate can always be distinguished from an expression enclosed by 
  parenthesis: this is a consequence of the fact that named notation is
  required for an aggregate with a single component"  LRM 4.3(8)

--Thor
dlc@ddsdx2.jhuapl.edu