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This page discusses cases where instantiating of a parameter collapses two generically different functions.

The page is connected to the thread http://groups.google.com/group/fricas-devel/browse_frm/thread/5097633953c6841d/c3cb9671206609f8#c3cb9671206609f8

On Tue, Mar 24, 2009 at 4:24 AM, Ralf Hemmecke wrote:

Aldor's libalgebra has some bugs in it that seem to be really hard to track down. I faintly remember one such bug that I could nearly assign to the coexistence of:

  *: (Integer, %) -> % and *: (R, %) -> %

where R is instantiated with Integer. The problem here is a hidden overloading of implementations. Suppose you implement something like

fricas
(1) -> <aldor>
#include "axiom"
MyWeirdPoly(R: Ring): Ring with { *: (Integer, %) -> %; *: (R, %) -> %; coerce: R -> %; -- ... } == Integer add { coerce(r:R):% == r pretend %; ((i: Integer) * (x: %)): % == ((i+i)::%)*x; ((r: R) * (x: %)): % == (r::%) * x -- ... }</aldor>
fricas
Compiling FriCAS source code from file 
      /var/lib/zope2.10/instance/axiom-wiki/var/LatexWiki/6603601906039884450-25px001.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/6603601906039884450-25px001.as", line 1: 
#include "axiom"
^
[L1 C1] #1 (Error) Could not open file `axiom'.
The )library system command was not called after compilation.

fricas
)show MyWeirdPoly
The )show system command is used to display information about types or partial types. For example, )show Integer will show information about Integer .
MyWeirdPoly is not the name of a known type constructor. If you want to see information about any operations named MyWeirdPoly , issue )display operations MyWeirdPoly

fricas
p:=1$MyWeirdPoly(Integer)
There are no library operations named MyWeirdPoly Use HyperDoc Browse or issue )what op MyWeirdPoly to learn if there is any operation containing " MyWeirdPoly " in its name.
Cannot find a definition or applicable library operation named MyWeirdPoly with argument type(s) Type
Perhaps you should use "@" to indicate the required return type, or "$" to specify which version of the function you need.

Now lets try the same thing in SPAD

spad
)abbrev package MWP2 MyWeirdPoly2
MyWeirdPoly2(R: Ring): Ring with
  _*: (Integer, %) -> %
  _*: (R, %) -> %
  coerce: R -> %
  -- ...
 == Integer add
  coerce(r:R):% == r pretend %
  ((i: Integer) * (x: %)): % == ((i+i)::%)*x
  ((r: R) * (x: %)): % == (r::%) * x
  -- ...
spad
   Compiling FriCAS source code from file 
      /var/lib/zope2.10/instance/axiom-wiki/var/LatexWiki/4436499139492326087-25px004.spad
      using old system compiler.
   MWP2 abbreviates package MyWeirdPoly2 
------------------------------------------------------------------------
   initializing NRLIB MWP2 for MyWeirdPoly2 
   compiling into NRLIB MWP2 
   compiling exported coerce : R -> %
      MWP2;coerce;R%;1 is replaced by r 
Time: 0 SEC.
compiling exported * : (Integer,%) -> % Time: 0 SEC.
compiling exported * : (R,%) -> % Time: 0 SEC.
(time taken in buildFunctor: 0)
;;; *** |MyWeirdPoly2| REDEFINED
;;; *** |MyWeirdPoly2| REDEFINED Time: 0 SEC.
Cumulative Statistics for Constructor MyWeirdPoly2 Time: 0 seconds
--------------non extending category---------------------- .. MyWeirdPoly2(#1) of cat (|Join| (|Ring|) (CATEGORY |domain| (SIGNATURE * (% (|Integer|) %)) (SIGNATURE * (% |#1| %)) (SIGNATURE |coerce| (% |#1|)))) has no (|IntegerNumberSystem|) finalizing NRLIB MWP2 Processing MyWeirdPoly2 for Browser database: --->-->MyWeirdPoly2(constructor): Not documented!!!! --->-->MyWeirdPoly2((* (% (Integer) %))): Not documented!!!! --->-->MyWeirdPoly2((* (% R %))): Not documented!!!! --->-->MyWeirdPoly2((coerce (% R))): Not documented!!!! --->-->MyWeirdPoly2(): Missing Description ; compiling file "/var/aw/var/LatexWiki/MWP2.NRLIB/MWP2.lsp" (written 07 DEC 2024 06:22:16 AM):
; wrote /var/aw/var/LatexWiki/MWP2.NRLIB/MWP2.fasl ; compilation finished in 0:00:00.008 ------------------------------------------------------------------------ MyWeirdPoly2 is now explicitly exposed in frame initial MyWeirdPoly2 will be automatically loaded when needed from /var/aw/var/LatexWiki/MWP2.NRLIB/MWP2

fricas
)show MyWeirdPoly2
MyWeirdPoly2(R: Ring) is a domain constructor Abbreviation for MyWeirdPoly2 is MWP2 This constructor is exposed in this frame. ------------------------------- Operations --------------------------------
?*? : (R, %) -> % ?*? : (Integer, %) -> % ?*? : (%, %) -> % ?*? : (PositiveInteger, %) -> % ?+? : (%, %) -> % -? : % -> % ?-? : (%, %) -> % ?=? : (%, %) -> Boolean 1 : () -> % 0 : () -> % ?^? : (%, PositiveInteger) -> % annihilate? : (%, %) -> Boolean antiCommutator : (%, %) -> % associator : (%, %, %) -> % coerce : R -> % coerce : Integer -> % coerce : % -> OutputForm commutator : (%, %) -> % latex : % -> String one? : % -> Boolean opposite? : (%, %) -> Boolean recip : % -> Union(%,"failed") sample : () -> % zero? : % -> Boolean ?~=? : (%, %) -> Boolean ?*? : (NonNegativeInteger, %) -> % ?^? : (%, NonNegativeInteger) -> % characteristic : () -> NonNegativeInteger leftPower : (%, NonNegativeInteger) -> % leftPower : (%, PositiveInteger) -> % leftRecip : % -> Union(%,"failed") rightPower : (%, NonNegativeInteger) -> % rightPower : (%, PositiveInteger) -> % rightRecip : % -> Union(%,"failed") subtractIfCan : (%, %) -> Union(%,"failed")

fricas
q:=1$MyWeirdPoly2(Integer)

\label{eq1}1(1)
Type: MyWeirdPoly2?(Integer)
fricas
3*q

\label{eq2}3(2)
Type: MyWeirdPoly2?(Integer)

Surprise!

SPAD produces the opposite result from Aldor.




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