MathAction SandBox Cast

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This is an example of using pretend to perform a type unsafe operation.

The follow commands are run using FriCAS

axiom

)version

Value = "Sunday November 1, 2009 at 20:31:03 "

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)

spad

   Compiling FriCAS source code from file 
      /var/zope2/var/LatexWiki/76482798552469661-25px002.spad using old
      system compiler.
   CAST abbreviates package cast 
------------------------------------------------------------------------
   initializing NRLIB CAST for cast 
   compiling into NRLIB CAST 
   compiling exported cast1 : Integer -> Float
      CAST;cast1;IF;1 is replaced by LETji 
Time: 0.03 SEC.

(time taken in buildFunctor:  0)

;;;     ***       |cast| REDEFINED

;;;     ***       |cast| REDEFINED
Time: 0 SEC.

   Cumulative Statistics for Constructor cast
      Time: 0.03 seconds

   finalizing NRLIB CAST 
   Processing cast for Browser database:
--->-->cast((cast1 ((Float) (Integer)))): Not documented!!!!
--->-->cast(constructor): Not documented!!!!
--->-->cast(): Missing Description
; compiling file "/var/zope2/var/LatexWiki/CAST.NRLIB/CAST.lsp" (written 11 MAY 2010 11:14:38 PM):
; compiling (/VERSIONCHECK 2)
; compiling (PUT (QUOTE |CAST;cast1;IF;1|) ...)
; compiling (DEFUN |CAST;cast1;IF;1| ...)
; compiling (DEFUN |cast| ...)
; compiling (DEFUN |cast;| ...)
; compiling (MAKEPROP (QUOTE |cast|) ...)
; compiling (MAKEPROP (QUOTE |cast|) ...)

; /var/zope2/var/LatexWiki/CAST.NRLIB/CAST.fasl written
; compilation finished in 0:00:00.052
------------------------------------------------------------------------
   cast is now explicitly exposed in frame initial 
   cast will be automatically loaded when needed from 
      /var/zope2/var/LatexWiki/CAST.NRLIB/CAST

This command used to cause a "memory may be damaged" error::

axiom

cast1(1)$CAST

   >> System error:
   The value 1 is not of type CONS.

aldor

#include "axiom"
cast2(i: Integer): Float == {
      j:Float := (i pretend Float)
}

aldor

   Compiling FriCAS source code from file 
      /var/zope2/var/LatexWiki/casta.as using AXIOM-XL compiler and 
      options 
-O -Fasy -Fao -Flsp -laxiom -Mno-ALDOR_W_WillObsolete -DAxiom -Y $AXIOM/algebra -I $AXIOM/algebra
      Use the system command )set compiler args to change these 
      options.
   Compiling Lisp source code from file ./casta.lsp
   Issuing )library command for casta
   Reading /var/zope2/var/LatexWiki/casta.asy

This command also used cause a "memory may be damaged" error::

axiom

cast2(1)

   >> System error:
   The value 1 is not of type CONS.

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