Re: need help learning Ada for a modula-2 programmer

[Jeffrey Carter <spam.jrcarter.not@spam.not.acm.org>]

On 02/01/2014 07:47 PM, agent@drrob1.com wrote:
>
> PROCEDURE GetCommandLine(CommandLine : OUT String) is
> BEGIN
>    n := argument_count;
>    k := 1;
>
>    WHILE k <= n LOOP
>      move(argument(k),argstr);   -  tried this-
>      argstr := argument(k);         -- and this.  Neither works.

Where is Argstr defined?

>      cmdlinefrag := cmdlinefrag & argstr;

Same for Cmdlinefrag.

> I don't understand how to get this working using standard strings.
> This is easy for me using ARRAY OF CHARACTER types in M2 and
> procedures from the Strings standard module.

The actual length of Commandline is determined by the actual parameter. If you 
want to return a String of just the right length, you'll either need an out 
parameter of an (Un)Bounded_String type, or a function that returns String.

For the latter approach, you could use recursion:

function Command_Line return String is
    function Piece (Arg : in Positive) return String is
       -- Empty declarative part
    begin -- Piece
       if Arg > Ada.Command_Line.Argument_Count then
          return "";
       elsif Arg = Ada.Command_Line.Argument_Count then
          return Ada.Command_Line.Argument (Arg);
       else
          return Ada.Command_Line.Argument (Arg) & ' ' & Piece (Arg + 1);
       end if;
    end Piece;
begin -- Command_Line
    return Piece (1);
end Command_Line;

-- 
Jeff Carter
"I'm particularly glad that these lovely children were
here today to hear that speech. Not only was it authentic
frontier gibberish, it expressed a courage little seen
in this day and age."
Blazing Saddles
88