Duplicate an entry if possible.
Duplicate an entry if possible. If t1 has a memoised value associated
with it, set the value associated with t2 to the same value. If there
is no value associated with t1, set the value associated with t2 to
u.
Return the value stored at key t as an option.
Return the value stored at key t if there is one, otherwise
return u.
Has the value of this attribute at t already been computed or not?
By default, does the memo table contain a value for t?
Store the value u under the key t.
Store the value u under the key t if t does not already have an
associated value.
Immediately reset the memo table.
Immediately reset the memo table at t.
Check to see if a reset has been requested via the common memo version, and if so, do it.
Common interface for encapsulation of memoisation for a single memoised entity backed by a configurable cache.