Re: [igraph] perl bindings

[Tamas Nepusz]

Hi John,

> 1) Make a simple binding of igraph data types to perl
> objects (and maybe add named arguments etc, which is fairly
> easy, but would require more hand coding). But perl has no
> native C-,Fortran- like array type, so flexible IO, etc. would
> be problematic.  Did someone say python does have such a native
> data type ?
Well, Python does have an array-like data type in the NumPy (Numeric Python) 
module, but this is not part of Python's standard library and igraph does not 
use it. igraph simply uses standard Python lists in place of igraph_vector_t 
objects and they are converted on-the-fly to igraph_vector_t before calling an 
internal igraph function. Lists of lists are converted to igraph_matrix_t. 
Basically, for most of igraph's internal data types, the source code of the 
Python interface contains a conversion function that takes an arbitrary Python 
object and decides whether it can be converted to the target igraph data type. 
If so, it also does the conversion, if not, it raises the appropriate Python 
exception which is then propagated back to the Python interpreter. The actual 
methods of the Graph class in Python then simply call the conversion functions 
for each input argument, call the appropriate igraph function with the 
converted arguments, then take the result and convert them back to Python. It 
is so straightforward that it could even have been generated by a script; in 
fact, the vast majority of the code for the R interface is generated by 
tools/stimulus.py in the source tree, which takes the interface definitions 
from interfaces/functions.def and some code snippets from 
interfaces/R/types-C.def and interfaces/R/types-R.def. If you decide to build a 
Perl interface for igraph, consider hacking tools/stimulus.py (by extending it 
with a Perl code generator based on the already existing R and Java code 
generators) and using that instead of coding your interface manually.

-- 
Tamas