[Axiom-developer] Re: [Axiom-mail] Assigning to Element of Array of Records Doesn't Seem to Work

[Ralf Hemmecke]

I think you have just found a bug in the Axiom interpreter/compiler.

The following Aldor program compiles fine.

aldor -fx -laldor aaa.as

and gives as output

xs = [
  [0, 0]
  [0, 0]
  [10, 0]
]

ys = [
  [0, 0]
  [0, 0]
  [10, 0]
]

Don't be distracted by this output stuff (TextWriter). Your code 
basically appears in the main() function. And in Aldor that works.

Since this special form of assignment is actually a call to the function 
set! (Aldor) the line

  ys(2).k := 10;

is equivalent to

  set!(ys(2), k, 10);

There is no problem with the actual form of the first argument of set!. 
As long as there is a function

  set!: (R, Enumeration(k: Type), INT) -> INT

that should compile fine. Well, and "ys(2)" is of type R.
(Of course, all this is Aldor specific, but Axiom should try hard to get 
close.)

I have no idea, though, why Axiom is unable to deal correctly with that 
expression. That should be dealt with by our compiler experts.

Ralf




---BEGIN aaa.as
#include "aldor"
#include "aldorio"

INT == MachineInteger;
R ==> Record(k: INT, rad: INT);
import from R, INT;

initrec(): R == [0,0];

(tw: TextWriter) <= (r: R): TextWriter == {
  tw << "[" << r.k << ", " << r.rad << "]"
}
(tw: TextWriter) << (g: Generator R): TextWriter == {
  tw << "[" << newline;
  for r in g repeat tw << "  " <= r << newline;
  tw << "]" << newline;
}


main(): () == {
  xs: List R := [initrec() for i in 1..3];
  ys: Array R := [z for z in xs];
  ys(2).k := 10;
  stdout << "xs = " << generator xs << newline;
  stdout << "ys = " << generator ys << newline;
}

main();---END aaa.as

On 08/08/2007 11:41 AM, Bill Wood wrote:
> I'm just trying to assign to a field of a record in a one-dimensional
> array of records, but I get this incomprehensible message:
> =====================================================================
> (1) -> )clear all
>    All user variables and function definitions have been cleared.
> (1) -> )read foo.input
> -- File of Axiom definitions solving problem 124.
> -- Created 2007/08/08 by Bill Wood.
>
> init_rec() ==
>   r : Record(k: INT, rad: INT) := [0,0]
>   r
>
>                                            Type: Void
> (2) -> xs := [init_rec() for i in 1..3]
>    Compiling function initrec with type () -> Record(k: Integer,rad:
>       Integer)
>
>    (2)  [[k= 0,rad= 0],[k= 0,rad= 0],[k= 0,rad= 0]]
>                       Type: List Record(k: Integer,rad: Integer)
> (3) -> ys := oneDimensionalArray(xs)
> (3) ->
>    (3)  [[k= 0,rad= 0],[k= 0,rad= 0],[k= 0,rad= 0]]
>            Type: OneDimensionalArray Record(k: Integer,rad: Integer)
> (4) -> ys
> (4) ->
>    (4)  [[k= 0,rad= 0],[k= 0,rad= 0],[k= 0,rad= 0]]
>            Type: OneDimensionalArray Record(k: Integer,rad: Integer)
> (5) -> ys(2).k := 10
>  5) ->
>    The form on the left hand side of an assignment must be a single
>       variable, a Tuple of variables or a reference to an entry in an
>       object supporting the setelt operation.
> (5) ->
> =======================================================================
> What do I have to do to set the fields of the records to desired
> values???
>
>  -- Bill Wood