use ispredicate(::Arbfunction) to return Bool from arbcall

[kalmarek]

This adds just predicate detection and uses it to turn the returned int to Bool. Arblib returns "success", hence non-zero output can be interpreted as true

[Joel-Dahne]

This looks good! Would be good to also add some simple tests, should be easy since ispredicate is self contained.

[saschatimme]

@kalmarek In which branch do you want to merge this by now? Shouldn't this be master?

[kalmarek]

@Joel-Dahne I know it's post-factum, but could you produce a list with your (canonical ;) version of arb docs which functions are detected as predicates? I made this list locally and everything looked ok, but you never know ;)

[Joel-Dahne]

@Joel-Dahne I know it's post-factum, but could you produce a list with your (canonical ;) version of arb docs which functions are detected as predicates? I made this list locally and everything looked ok, but you never know ;)

I looked through the functions detected as predicates and it seems fully correct! However it does miss some functions which do return a boolean, for example arb_mat_solve, but this is probably fine. I can give a precise list as well, but that probably makes more sense to do after #32 is merged since much more functions will be parsed.

[kalmarek]

I think that the return value of arb_mat_solve (also of e.g. eig_simple) is more of an error code than a Bool, but we can discuss this and change it later. Indeed the ispredicate would become much simpler, since there are only a few exceptions to the Cint → Bool translation upon return (e.g. *_cmp function).

see #62