Re: How to check for availability of functions in core octave

[Ben Abbott]

On Jul 29, 2011, at 5:44 PM, Philip Nienhuis wrote:

> John W. Eaton wrote:
>> On 29-Jul-2011, PhilipNienhuis wrote:
>> 
>> | Almost, Ben, a good first try, thanks.
>> |
>> | But... your example also picks up functions in octave-forge:
>> |
>> | octave.exe:4>  isimplemented = @(fun) exist (strcat(fun,".m")) == 2 || 
>> exist
>> | (fun)>  2
>> | isimplemented =
>> |
>> | @(fun) exist (strcat (fun, ".m")) == 2 || exist (fun)>  2
>> |
>> | octave.exe:5>  isimplemented ("residue")
>> | ans =  1
>> | octave.exe:6>  isimplemented ("xls2oct")
>> | ans =  1
>> |
>> | (xls2oct.m is in the OF io package)
>> |
>> | Even worse, it picks up OF functions shadowing core functions:
>> |
>> | GNU Octave, version 3.4.2
>> | Copyright (C) 2011 John W. Eaton and others.
>> | This is free software; see the source code for copying conditions.
>> | There is ABSOLUTELY NO WARRANTY; not even for MERCHANTABILITY or
>> | FITNESS FOR A PARTICULAR PURPOSE.  For details, type `warranty'.
>> |<snip>
>> | warning: function
>> | C:\Programs\Octave\3.4.2\share\octave\packages\specfun-1.0.9\erfcx.m sha
>> | dows a built-in function
>> | :
>> |<further down>
>> | :
>> | octave.exe:7>  isimplemented ("erfcx")
>> | ans =  1
>> | octave.exe:8>
>> |
>> |
>> | My question is really aimed at detecting stuff in core Octave, regardless 
>> of
>> | whether it is shadowed or not (yes an extra requirement coming out of the
>> | blue, now that there's something I could try).
>> 
>> The shadow warning comes from a function in load-path.cc, when the
>> contents of a directory are being added to the internal map that
>> allows for function lookups.
>> 
>> You could use the results of __builtins__, __keywords__, and
>> __list_functions__, but you would need to be sure that the load path
>> contains only the default set of directories.  Maybe
>> __list_functions__ could be modified to accept a parameter telling it
>> to list only the "system" functions?
> 
> Such a parameter would be a good option.
> 
> An alternative is excluding all paths in .../share/octave/packages/ ? (as 
> that is where most of the shadowing I'm after comes from) and then re-running 
> __list_functions__
> 
> Trying something along these lines:
> 
> pkg unload all
> __list_functions__
> 
> reveals that __list_functions__ appears to read from cached info. All 
> octave-forge functions are still listed.
> 
> Can __list_functions__'s base info be reinitialized? If so I would be almost 
> there.
> 
> Philip

If functions in the current working directory aren't a problem, then you can do 
something like ...

function [ ret ] = isimplemented (fun)
  path_orig = path ();
  unwind_protect
    restoredefaultpath ();
    ret = exist (strcat(fun,".m")) == 2 || exist (fun) > 2;
  unwind_protect_cleanup
    path (path_orig)
  end_unwind_protect
endfunction

Ben