There is a very preliminary interface to create parallel threads.
The interface is similar to the standard delay/force,
where a thread is basically the same as a promise, except that
evaluation may be in parallel.
Syntax: future expression
Creates a new thread that evaluates expression.
(The result extends java.lang.Thread and
implements gnu.mapping.Lazy.)
Procedure: force thread
The standard force function is generalized to also work
on threads. It waits for the thread’s expression to finish
executing, and returns the result.
Procedure: runnable function
Creates a new Runnable instance from a function.
Useful for passing to Java code that expects a Runnable.
You can get the result (a value or a thrown exception) using the
getResult method.
Syntax: synchronized object form ...
Synchronize on the given object. (This means getting an
exclusive lock on the object, by acquiring its monitor.)
Then execute the forms while holding the lock.
When the forms finish (normally or abnormally by throwing
an exception), the lock is released.
Returns the result of the last form.
Equivalent to the Java synchronized statement,
except that it may return a result.
