8.3 Persistent Functors

Not only can you create functors interactively, but you can also save them in files. We call this ``making functors persistent''. Consider our earlier functor Foo. We can save it to file /tmp/Foo.ozf as follows:

{Pickle.save Foo "/tmp/Foo.ozf"}

A persistent value is also called a pickle, hence the name Pickle for the module providing the API for persistent values. Note the extension ozf for the file in which we saved our functor: this is the extension conventionally chosen for persistent functors. The advantage of a persistent functor is that it can be reused:

declare [M]={Module.link ['/tmp/Foo.ozf']}
{M.greet}

Even more interestingly, it can be reused as an import in an other module:

declare 
functor Baz 
import GreetModule at '/tmp/Foo.ozf' 
export GreetTwice
define 
   proc {GreetTwice}
      {GreetModule.greet}
      {GreetModule.greet}
   end 
end 
 
declare [M]={Module.apply [Baz]}
{M.greetTwice}