tricu

An interpreted language for exploring Tree Calculus
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1d81c9b0665494ef2acdfc60a3b4c243518121dc5a7a35bdb4a31244eee5f076.tri (2191B)

      1 !import prelude *
      2 !import io *
      3 !export *
      4 
      5 -- Interaction Tree Effect Runtime
      6 --
      7 -- The IO system is an interaction-tree effect runtime interpreted by a
      8 -- small-step machine with a cooperative scheduler.  Primitive actions
      9 -- (putStr, readFile, writeFile, ...) are tagged nodes in an interaction
     10 -- tree.  Sequencing is performed by the single generic `bind` constructor.
     11 --
     12 --   pure x            -- lift a pure value into IO
     13 --   bind action k     -- run action, then apply k to its result
     14 --   thenIO a b        -- run a, discard its result, then run b
     15 --   mapIO action f    -- run action, then apply f to its result inside pure
     16 --
     17 -- The runtime supports several effects beyond basic IO:
     18 --   ask               -- read the current environment
     19 --   local f action    -- run action with environment transformed by f
     20 --   get               -- read the current mutable state
     21 --   put s             -- replace the mutable state
     22 --   fork action       -- spawn a concurrent task, returning a handle
     23 --   await handle      -- wait for a forked task to complete
     24 --   yield             -- yield control to the scheduler
     25 --   sleep ms          -- suspend current task for N milliseconds
     26 --
     27 -- File operations return a Result tree (see lib/base.tri):
     28 --   ok value     -- pair true  (pair value t)
     29 --   err msg      -- pair false (pair msg   t)
     30 --
     31 -- Use onReadFile / onWriteFile for convenient branching.
     32 --
     33 -- See demos/interactionTrees/ for smaller focused examples.
     34 
     35 -- Cooperative async demo.
     36 --   fork runs an action in the background.
     37 --   sleep suspends the current task for N milliseconds.
     38 --   await waits for a forked task and returns its value.
     39 --
     40 --   Here the child sleeps for 2 s while the parent prints immediately.
     41 --   The parent's message appears first, proving interleaving.
     42 
     43 asyncDemo = (
     44   bind (fork
     45     (bind (sleep 2000) (_ :
     46     bind (putStrLn "2000ms done sleeping!") (_ :
     47     pure "child2000 done"))))
     48   (handle2000 :
     49   bind (fork
     50     (bind (sleep 5000) (_ :
     51     bind (putStrLn "5000ms done sleeping!") (_ :
     52     pure "child5000 done"))))
     53   (handle5000 :
     54   bind (putStrLn "Parent first!") (_ :
     55   bind (await handle5000) (_ :
     56   await handle2000)))))
     57 
     58 main = io asyncDemo