From help-octave-request at bevo dot che dot wisc dot edu  Wed Apr 21 17:35:05 1999
Subject: Re: An engine for octave
From: Jesse Bennett <jbennett at raytheon dot com>
To: mxu1 at broadway dot GC dot cuny dot edu, help-octave@bevo.che.wisc.edu
Date: Wed, 21 Apr 1999 17:37:41 -0500 (CDT)

Min,

I have a working engine for Octave which implements the following Matlab C
API functions:

engOpen
engClose
engGetFull
engPutFull
engEvalString
engOutputBuffer

I have been meaning to clean it up and submit it to the Octave sources
mailing list, but I just haven't found the time.  Basically, it works by
forking, initializing pipes for stdin/stdout, then exec'ing Octave. 
Commands are then sent to the engine as if they were typed at the command
line. 

The only problem I had with this approach is that there is not a good way
in Octave to "load" a file from stdin (needed by engPutFull).  IIRC, the
load will not terminate without an EOF, and the EOF character causes
Octave to close stdin (or something like that, I never got around to
investigating the problem in detail).  In any case, only the first load
succeeds with this method.  The workaround I used was to create a fifo,
and then pass the data through it. This is not a portable approach, since
some UNIX systems will not allow ordinary users to create fifos.  A
temporary file could also be used, but this is messy as well.  It would be
nice if someone created a patch for Octave that allows `load -ascii "-"'
to work (at least for a single matrix). 

What I have works, but it is basically a hack that sorely needs improving. 
There is very little error checking, and if the calling C program exits or
dies without closing the engine it has to be killed manually.

Since it seems others are interested in this, I will try to get it
organized this weekend and post the code on the sources list.

Jesse Bennett


On March 31, 1999, Min Xu wrote:

> I am considering an engine for octave which may open an instance of
> octave, do any number of fevals, and exchange of data between the
> calling C/C++ program and the octave instance, and surely close the
> instance when done.

[snip]

> I checked the help-octave archive. It seems that the interest of
> embedding octave in another environment is always high. Has anyone
> done anything in that?  If not, I will code one.