On Monday, October 16, 2006 7:30 PM Gabriel Dos Reis wrote:

Consider the following code snipet::

(1) -> <spad>

)abbrev domain T T

Decl := Record(name: Symbol, type: T)

T(): Public == Private where
  Public ==> with
    type: Symbol -> %
    decl: (Symbol, %) -> Decl
  Private ==> add
    decl(n,t) == [n,t]</spad>

Compiling FriCAS source code from file 
      /var/lib/zope2.10/instance/axiom-wiki/var/LatexWiki/9110329210505148464-25px001.spad
      using old system compiler.
   T abbreviates domain T 

   >> Apparent user error:
   Parsing error: illegal toplevel form

The SPAD compiler complains on the definition of decl with the message [click on + to expand compiler output]

On Mon, 16 Oct 2006, Page, Bill wrote:

  Why would you consider the type T itself to be known in the scope
  where the value of Decl is computed?

Gaby's Reply:

  Because inside the definition of T(), % is supposed to refer to the
  domain defined, i.e. T.

Yes that is correct. But you are asking SPAD explicitly to evaluate Record(name: Symbol, type: T) outside of and prior to the definition of T(). It seems that in the normal mode of operation of the SPAD compiler this is out of context for T. (But see how this can be changed below.)

Gaby said:

  Notice that the only thing that is needed to be known is the type
  name.

I think it is instructive to see what Aldor says about this construction:

  Decl := Record(name: Symbol, type: T)
  ^
  [L4 C1] #7 (Error) `Decl' is used in a type, so must be constant,
    and so cannot be assigned to.

After correcting the definition, Aldor compiles this thing without complaint:

#pile
#include "axiom"

Decl == Record(name: Symbol, type: T)

T: Public == Private where
  Public ==> with
    type: Symbol -> %
    decl: (Symbol, %) -> Decl
  Private ==> add
    decl(n:Symbol,t:%):Decl == [n,t]
    type(x:Symbol):% == x pretend %

   Compiling FriCAS source code from file 
      /var/lib/zope2.10/instance/axiom-wiki/var/LatexWiki/1501044709281826201-25px002.as
      using Aldor compiler and options 
-O -Fasy -Fao -Flsp -lfricas -Mno-ALDOR_W_WillObsolete -DFriCAS -Y $FRICAS/algebra -I $FRICAS/algebra
      Use the system command )set compiler args to change these 
      options.
"/var/lib/zope2.10/instance/axiom-wiki/var/LatexWiki/1501044709281826201-25px002.as", line 2: 
#include "axiom"
^
[L2 C1] #1 (Error) Could not open file `axiom'.

   The )library system command was not called after compilation.

Even more exciting is the fact that using the $bootStrapMode flag discovered by Waldek the same code is compiled by SPAD without complaint!

)lisp (setq |$bootStrapMode| t)
)abbrev domain T T

Decl == Record(name: Symbol, type: T)

T(): Public == Private where
  Public ==> with
    type: Symbol -> %
    decl: (Symbol, %) -> Decl
  Private ==> add
    decl(n:Symbol,t:%):Decl == [n,t]
    type(x:Symbol):% == x pretend %

   Compiling FriCAS source code from file 
      /var/lib/zope2.10/instance/axiom-wiki/var/LatexWiki/575440422302135301-25px003.spad
      using old system compiler.
   Your user access level is compiler and this command is therefore not
      available. See the )set userlevel command for more information.
   T abbreviates domain T 
------------------------------------------------------------------------

   Decl is an unknown constructor and so is unavailable. Did you mean 
      to use -> but type something different instead?

The same code which gives the above error:

  >> System error:
   Caught fatal error [memory may be damaged]

works when compiled in a clean Axiom session. See [SandBoxBootStrap2]?.

I wonder why $bootStrapMode t is not the normal default mode of operation for SPAD? Is the generated code less efficient?

Bill Page wrote:

Perhaps you meant to write:

      Decl := Record(name: Symbol, type: %)

Gaby asked:

  what would that % refers to?

As far as I know, in SPAD the Type % is not resolved statically at compile time instead it remains a placeholder for "this domain" in whatever context it occurs. (In contrast to Aldor.)

Bill Page claimed:

  which seems to compile as expected?

Gaby:

  But, we don't know the compiler is right.  Which is I'm asking.

I don't know. Maybe you need to extend your example to actually do some computation which tests the semantics and/or take a look at the generated Lisp code.