fix graph.formula()

[maelle]

A bit of a hack, but it works to simply do what graph_from_literal() does.

library("igraph")
#> 
#> Attaching package: 'igraph'
#> The following objects are masked from 'package:stats':
#> 
#>     decompose, spectrum
#> The following object is masked from 'package:base':
#> 
#>     union
graph.formula(x -+ z, z -+ y, x -+ y, y -+ x) 
#> Warning: `graph.formula()` was deprecated in igraph 2.0.0.
#> ℹ Please use `graph_from_literal()` instead.
#> This warning is displayed once every 8 hours.
#> Call `lifecycle::last_lifecycle_warnings()` to see where this warning was
#> generated.
#> IGRAPH c33a34d DN-- 3 4 -- 
#> + attr: name (v/c)
#> + edges from c33a34d (vertex names):
#> [1] x->z x->y z->y y->x
graph_from_literal(x -+ z, z -+ y, x -+ y, y -+ x)
#> IGRAPH 5ccefd2 DN-- 3 4 -- 
#> + attr: name (v/c)
#> + edges from 5ccefd2 (vertex names):
#> [1] x->z x->y z->y y->x

^{Created on 2024-01-08 with reprex v2.0.2}

[maelle]

@krlmlr if this is ok, I'll integrate it to the PR in igraph/rigraph (which I'll then have to rebase)

[maelle]

But I'd do the rebasing at the very very end since this is not an automatic change, or I'd edit the script to make this a special case in the automatic PR creation.

[krlmlr]

I merged the better part of your big PR already, only two commits are remaining. Do we really need to rerun the script? I'd be fine with manual changes. Am I missing anything?

[krlmlr]

Yes, this is what I mean by "inlining a function".

[maelle]

Yes, this is what I mean by "inlining a function".

Aaaah this makes sense now, thanks. Some of them are a bit long so I'll have to think about how to best do it (later this week or next)

I realized later manual changes would be fine.