phc interface not working in Sage version 8.0

[Peter Mueller]

Trying the example from the doc of phc results in:

sage: from sage.interfaces.phc import phc

sage: R.<x,y> = PolynomialRing(CDF,2)

sage: testsys = [x^2 + 1, x*y - 1]

sage: phc.mixed_volume(testsys)

---------------------------------------------------------------------------

ExceptionPexpect                          Traceback (most recent call last)

<ipython-input-6-ca20607a9185> in <module>()

----> 1 phc.mixed_volume(testsys)

/home/mueller/local/sage-8.0/local/lib/python2.7/site-packages/sage/interfaces/phc.pyc in mixed_volume(self, polys, verbose)                                    

    758             4

    759         """

--> 760         output_filename = self._output_from_command_list(['phc -m','4','n','n','n'], polys, verbose = verbose)                                          

    761 

    762         out = open(output_filename).read()

/home/mueller/local/sage-8.0/local/lib/python2.7/site-packages/sage/interfaces/phc.pyc in _output_from_command_list(self, command_list, polys, verbose)         

    452 

    453         # Create a phc process

--> 454         child_phc = pexpect.spawn(command_list[0])

    455         # feed it the commands

    456         child_phc.sendline('y')

/home/mueller/local/sage-8.0/local/lib/python2.7/site-packages/pexpect/pty_spawn.pyc in __init__(self, command, args, timeout, maxread, searchwindowsize, logfile, cwd, env, ignore_sighup, echo, preexec_fn, encoding, codec_errors, dimensions)                                                                               

    196             self.name = '<pexpect factory incomplete>'

    197         else:

--> 198             self._spawn(command, args, preexec_fn, dimensions)

    199 

    200     def __str__(self):

/home/mueller/local/sage-8.0/local/lib/python2.7/site-packages/pexpect/pty_spawn.pyc in _spawn(self, command, args, preexec_fn, dimensions)                     

    269         if command_with_path is None:

    270             raise ExceptionPexpect('The command was not found or was not ' +

--> 271                     'executable: %s.' % self.command)

    272         self.command = command_with_path                                

    273         self.args[0] = self.command

ExceptionPexpect: The command was not found or was not executable: phc.

sage: 

[Vincent Delecroix]

Do you have phc installed on your computer? The error message says that
there is no 'phc' command available...

(I was not able to install phcpack so I can not properly test the interface)

[Peter Mueller]

Thanks, that solved the problem. (I wasn't aware that the actual phc binary isn't included in sage while the interface to it is.)