On November 21, 2005 4:48 PM I wrote:
>
> It is pretty clear in the following example that the Axiom
> interpreter does something odd:
>
> (1) -> I:Integer
> Type: Void
> (2) -> F:Float:=1.0
>
> (2) 1.0
> Type: Float
> (3) -> I := F pretend Integer
>
> (3) 1()
> Type: Integer
> ...
> In the mean time we can certainly apply these same ideas to
> Spad and to the Spad-like programming language embedded in
> Axiom's interpreter.
>
> Gaby wrote:
> > Bill Page wrote:
> > | Yet the ability to use 'pretend' is critical to the concept
> > | of representation in the construction of Axiom domains.
> >
> > Indeed.
> >
> > | For a perhaps overly abstract discussion of this see:
> > |
> > | http://wiki.axiom-developer.org/RepAndPer
> > |
> > | So my question is: Does this feature of the Spad and Aldor
> > | languages actually make them "weakly typed"?
> >
>
> > In my mind "pretend" by itself does not make the language "weak
> > typed". It would make it so only if it "actively support" type
> > unsafe operations to be carried on with minimal effort -- in that
> > sense I would claim C is weakly typed. Notice here that my used
> > of "type safety" is not in a universal sense, but relatively to
> > Aldor's own semantics.
>
> Ok, so my example above from the Axiom interpreter (this is not
> what happens in Spad and Aldor) would be such an example of
> failure of type safety, right?
Here is the unhappy result of using 'pretend' this same way in
Spad:
(1) -> )sys cat cast.spad
)abbrev package CAST cast
cast(): exports == implementation where
exports == with
cast1: Integer -> Float
implementation == add
cast1(i:Integer):Float ==
j:Float := (i pretend Float)
(1) -> )compile cast.spad
Compiling AXIOM source code from file
/home/page/cast.spad
using old system compiler.
CAST abbreviates package cast
...
OPTIMIZE levels: Safety=0 (No runtime error checking), Space=0, Speed=3
Finished compiling /home/page/axiom/CAST.NRLIB/code.lsp.
------------------------------------------------------------------------
cast is already explicitly exposed in frame initial
cast will be automatically loaded when needed from
/home/page/CAST.NRLIB/code
(1) -> cast1(1)$CAST
>> System error:
Caught fatal error [memory may be damaged]
(1) ->
-----------
The same thing happens with Aldor:
(1) -> )sys cat casta.as
#include "axiom"
cast2(i: Integer): Float == {
j:Float := (i pretend Float)
}
(1) -> )compile casta.as
Compiling AXIOM source code from file /home/page/casta.as using
AXIOM-XL compiler and options
-O -Fasy -Fao -Flsp -laxiom -Mno-AXL_W_WillObsolete -DAxiom -Y
$AXIOM/algebra
Use the system command )set compiler args to change these
options.
#1 (Warning) Deprecated message prefix: use `ALDOR_' instead of `_AXL'
Compiling Lisp source code from file ./casta.lsp
Issuing )library command for casta
Reading /home/page/casta.asy
(1) -> cast2(1)
>> System error:
Caught fatal error [memory may be damaged]
---------
As you can see we do not get a compile time errors, but we
do get a run-time errors.
By your criteria above then, would you agree that this
example proves that both Spad and Aldor are in fact weakly
typed or type unsafe?
Or do I have to be more careful to define clearly what are
the Spad and Aldor semantics for the example code before I
can make such a claim?
Regards,
Bill Page.
_______________________________________________
Axiom-developer mailing list
Axiom-developer@nongnu.org
http://lists.nongnu.org/mailman/listinfo/axiom-developer
