openfst - can't figure out the first few commands to start coding

[DreeDrunk]

Hi there,

I am using the files from http://www.openfst.org/twiki/bin/view/FST/WebHome. Running on an Ubuntu 12.04 64bit system. I compile with
g++ -I/usr/local/include Example.cxx -L/usr/local/lib -lfst to specify the libraries. I am trying something like the following with an example-file from http://www.openfst.org/twiki/bin/view/FST/FstQuickTour#OperationExample: (the interesting thing are the first two lines for now)

#include <fst/fstlib.h>
using namespace fst;


// A vector FST is a general mutable FST
StdVectorFst fst;

// Adds state 0 to the initially empty FST and make it the start state.
fst.AddState(); // 1st state will be state 0 (returned by AddState)
fst.SetStart(0); // arg is state ID

// Adds two arcs exiting state 0.
// Arc constructor args: ilabel, olabel, weight, dest state ID.
fst.AddArc(0, StdArc(1, 1, 0.5, 1)); // 1st arg is src state ID
fst.AddArc(0, StdArc(2, 2, 1.5, 1));

// Adds state 1 and its arc.
fst.AddState();
fst.AddArc(1, StdArc(3, 3, 2.5, 2));

// Adds state 2 and set its final weight.
fst.AddState();
fst.SetFinal(2, 3.5); // 1st arg is state ID, 2nd arg weight

Now I do not understand the error messages. Perhaps the problem isn't even openfst-specific?
Thanks in advance,
Greetings,
Dree

[dwhitney67]

Now I do not understand the error messages. Perhaps the problem isn't even openfst-specific?
Thanks in advance,
Greetings,
Dree

It would be of immense help if you would post the error messages!

P.S. Could the errors be related to the incomplete code that you have previously posted? For example, the code lacks a main() function.

[DreeDrunk]

You're so right! Thanks for the patience.
The following code

#include <fst/fstlib.h>
using namespace fst;

int main ()

{
// A vector FST is a general mutable FST
StdVectorFst fst;

// Adds state 0 to the initially empty FST and make it the start state.
fst.AddState(); // 1st state will be state 0 (returned by AddState)
fst.SetStart(0); // arg is state ID

// Adds two arcs exiting state 0.
// Arc constructor args: ilabel, olabel, weight, dest state ID.
fst.AddArc(0, StdArc(1, 1, 0.5, 1)); // 1st arg is src state ID
fst.AddArc(0, StdArc(2, 2, 1.5, 1));

// Adds state 1 and its arc.
fst.AddState();
fst.AddArc(1, StdArc(3, 3, 2.5, 2));

// Adds state 2 and set its final weight.
fst.AddState();
fst.SetFinal(2, 3.5); // 1st arg is state ID, 2nd arg weight

return 0;
}

produced the following error messages


dennis@DePeCe:~/Dokumente/OpenFST$ g++ -I/usr/local/include Example.cxx -L/usr/local/lib -lfst
/usr/local/lib/libfst.so: undefined reference to `dlerror'
/usr/local/lib/libfst.so: undefined reference to `dlopen'
collect2: ld gab 1 als Ende-Status zurück

I am german (and so is my system) so I have to translate the last line: "ld returned 1 as final status (or something like that)".

The lack of a main function was in my head already but I didn't see one program with these fst-thingy and so I wasn't sure if there is perhaps some special syntax that can replace a main function. But that was... crap, I think. Thanks again ;).

In case of my english being not as understandable as I hope, every word from a native speaker would be welcome :).

[dwhitney67]

It's always a pleasure to solve simple problems. It seems from your error posting that all you need to do is link with libdl.so (which contains the dynamic library loader software).

Try this:


g++ -I/usr/local/include Example.cxx -L/usr/local/lib -lfst -ldl

Note the -ldl at the end of the statement.

[DreeDrunk]

That solved the problem. Cool. ;).

The two statements
-lfst -ldl did the job for me. The order is essential. I am not sure, why I have to specify the lib with '-lfst' but I don't have to specify the folder of the header or lib files.

EDIT In the meantime I looked into the README file... ummm. I won't say one more word about that... *shame*