Hello,

I am quite new to igraph, so please be gentle :-)

I'm using the R interface, but I also looked at the C interface.  If I got
it right, in the C interface vertex indices start from 0, while in R they
start from 1 (that's good and natural for R).

However, the get.isomorphism functions return zeros in the mappings, e.g.

> g1=graph.edgelist(cbind(c(1,2,3,4),c(2,3,4,1)))
> g2=graph.edgelist(cbind(c(2,4,1,3),c(4,1,3,2)))

> graph.get.isomorphisms.vf2(g1,g2)
[[1]]
[1] 0 2 1 3

[[2]]
[1] 1 3 2 0

[[3]]
[1] 2 0 3 1

[[4]]
[1] 3 1 0 2


This seems inconsistent with the 1-based indexing of R.

Also, some other functions return maps which don't use 0:

> graph.isomorphic.vf2(g1,g2)
$iso
[1] TRUE

$map12
[1] 1 3 2 4

$map21
[1] 1 3 2 4

Is this by design, or is it an oversight?

Szabolcs
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