Work in progress representation of a computation. This is mostly used to handle recursive types. While building a computation on a recursive type, one needs to have some computation available for the location where the type appears recursively. init will be called once on each new type_name met during the traversal of a type. Each time the same type is encountered again, get_wip_computation will be called. At the end of the traversal of that particular type, set_final_computation will be called, offering as a way to "close" the wip representation. 'a t can be mutable (and is likely to be in practice).

After a set_final_computation is performed and return a final computation C for a type_name, C will be memoized and returned for each further occurrences of the same type_name inside the typerep, going further on.

It might be interesting to inline some computation for a few typerep if they appear several times within a typerep. This parameters will allow one to tweak the sharing between multiple occurences of the same typename. share = true means no inlining.

Note that not sharing recursive types will lead the of_typerep function to loop forever. Be careful when setting this.

An example where it is not suitable to share everything for example is typestruct. The typestruct of an int is a simple constructor called Int, naming it once and using the name to refere to it later within the typestruct does not lead to a shorter typestruct, and is in fact less readable. The benefit of the sharing depends on the computation, its memory and building costs.