This package contains the "unambiguous choice" operator unamb, which wraps thread racing up in a purely functional, semantically simple wrapper.
Given any two arguments u and v that agree unless bottom, the value of unamb u v is the more terminating of u and v.
Operationally, the value of unamb u v becomes available when the earlier of u and v does.
The agreement precondition ensures unamb's referential transparency.
unamb and a sample use appeared in the paper Push-pull functional reactive programming.
I moved it to its own
package in order to encourage experimentation.
Note that unamb correctly implements the least-upper-bound operation (on information content), also known as "lub" or "(⊔)", but only for flat types (in which values are completely undefined or completely defined).
I suggest using the lub package instead of unamb.
(Also on GitHub.)