MathAction SandBox Cast

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  - SandBox Cast <-- You are here.

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

The follow commands are run using FriCAS

fricas

(1) -> )version

"FriCAS 1.3.12 compiled at Sat  7 Jun 23:54:49 CEST 2025"

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/lib/zope2.10/instance/axiom-wiki/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 SEC.

(time taken in buildFunctor:  0)
Time: 0 SEC.

   Cumulative Statistics for Constructor cast
      Time: 0 seconds

   finalizing NRLIB CAST 
   Processing cast for Browser database:
--->-->cast(constructor): Not documented!!!!
--->-->cast((cast1 ((Float) (Integer)))): Not documented!!!!
--->-->cast(): Missing Description
; compiling file "/var/aw/var/LatexWiki/CAST.NRLIB/CAST.lsp" (written 01 OCT 2025 08:47:50 AM):

; wrote /var/aw/var/LatexWiki/CAST.NRLIB/CAST.fasl
; compilation finished in 0:00:00.008
------------------------------------------------------------------------
   cast is now explicitly exposed in frame initial 
   cast will be automatically loaded when needed from 
      /var/aw/var/LatexWiki/CAST.NRLIB/CAST

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

fricas

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/lib/zope2.10/instance/axiom-wiki/var/LatexWiki/casta.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/casta.as", line 1: 
#include "axiom"
^
[L1 C1] #1 (Error) Could not open file `axiom'.

   The )library system command was not called after compilation.

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

fricas

cast2(1)

   There are no library operations named cast2 
      Use HyperDoc Browse or issue
                               )what op cast2
      to learn if there is any operation containing " cast2 " in its 
      name.

   Cannot find a definition or applicable library operation named cast2
      with argument type(s) 
                               PositiveInteger

      Perhaps you should use "@" to indicate the required return type, 
      or "$" to specify which version of the function you need.

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