Re: Unconstrained arrays

[slinky.cs.nyu.edu!slinky.cs.nyu.edu!nobody@nyu.edu (Robert Dewar)]

Jim Crigler suggests:                                   

       Viewers : str_array (1 .. 1) := str_array'(Creat("text_artist"));

No, no, no! The qualification is useful only to determine the type wanted,but
we know what type we want (str_array!) The trouble is that the expression
(Creat("Text_artists")) just isn't of that type, as I hope the previous
answers have made clear.

I would strongly suggest that people make a habit of testing out replies
to queries of this kind by doing trial compilations with a reasonable Ada
compiler. I certainly do (and I am supposed to know Ada!) I think this would
result in fewer correcter responses to technical queries.

In this case, I ran it on an Alsys version 5 compiler and got:

.       8  Viewers2 : src_array (1 .. 1) := src_array'(Create("text_artist"));
.                                                      <--------1--------->
.1   **IDE There is a type inconsistency in this expression.
.
.
.
.        =================================================== More Information =
=
.        -> The context requires the following type(s):
.            - MAIN.SRC_ARRAY at line  3, an array type of STANDARD.INTEGER
.        -> But the expression has the following type(s) :
.            - STANDARD.INTEGER
.        ======================================================================
=



A rather lengthy, but absolutely accurate, error message!
I also ran it under GNAT, and got:

     8.  Viewers2 : src_array (1 .. 1) := src_array'(Create("text_artist"));

						     |
							   
                                                     |
        error: expect type "src_array" in this context


which isn't quite so verbose as the Alsys message, but is also accurate.
Actually we generally operate in brief, Unix-compatible error message mode,
which gives:

"t.ada", line 8: error: expect type "src_array" in this context

We usually find that the error flags aren't needed, and in any case we have
added a column positioning feature to EMACS so that the error message handling
in EMACS will position the cursor to the point of the error flag.