Re: [Caml-list] Polymorphic variant to string?

[Jacques Garrigue <garrigue@math.nagoya-u.ac.jp>]

From: Chris Campbell <cyberdanx@gmail.com>

> Is there a general method for converting polymorphic variants to
> strings?  The method using camlp4 assumes the source is compiled with
> it, which is not the case.  Basically I want to print a list of
> variants if a unit tests fail, so we can see exactly the contents of
> the list at that point.

The internal representation of a polymorphic variant tag is a hash by
a given function (you can find it in typing/btype.ml)
So, if you have the list of all possible variant tags, and their hash
values, you just have to do a reverse lookup.
Note that in theory, you need a list by type, as some independent
types might map different tags to the same hash value, but in practice
this should not be a problem: the probability of conflict is low
enough.
And of course this only apply to variant tags, not to argument values.

Jacques Garrigue