Frege

Frege is an open source programming language created in 2011.

Source code:

git clone https://github.com/frege/frege

#178on PLDB

13Years Old

223Repos

Frege is a non-strict, purely functional programming language for the Java virtual machine in the spirit of Haskell. It is considered a Haskell dialect or simply "a" Haskell for the Java virtual machine. Frege has a strong static type system with type inference. Read more on Wikipedia...

Frege website
Frege Wikipedia page
Frege is developed on GitHub and has 3,546 stars
Frege docs
There are at least 223 Frege repos on GitHub
Frege first developed in https://github.com/Frege
file extensions for Frege include fr
Frege on Twitter
The Google BigQuery Public Dataset GitHub snapshot shows 142 users using Frege in 160 repos on GitHub
There are 3 Project Euler users using Frege
Explore Frege snippets on Rosetta Code
GitHub supports syntax highlighting for Frege
See also: (7 related languages)Haskell, JVM, Java, Java Bytecode, Linux, Unix, Eclipse

Example from Linguist:

{-- 
    This program displays the
    current time on stdandard output
    every other second.
    -}
    
module examples.CommandLineClock where

data Date = native java.util.Date where
    native new :: () -> IO (MutableIO Date)     -- new Date()
    native toString :: Mutable s Date -> ST s String    -- d.toString()

--- 'IO' action to give us the current time as 'String'
current :: IO String
current = do
    d <- Date.new ()
    d.toString

{- 
    "java.lang.Thread.sleep" takes a "long" and
    returns nothing, but may throw an InterruptedException.
    This is without doubt an IO action.
    
    public static void sleep(long millis)
                  throws InterruptedException
    
    Encoded in Frege:
    - argument type  long   Long
    - result         void   ()
    - does IO               IO ()
    - throws ...            throws ....
     
-}
-- .... defined in frege.java.Lang
-- native sleep java.lang.Thread.sleep :: Long -> IO () throws InterruptedException

      
main args =  
    forever do
        current >>= print
        print "\r"
        stdout.flush
        Thread.sleep 999

Example from Wikipedia:

{-- 
    This program displays the
    current time on standard output
    every other second.
    -}
    
module examples.CommandLineClock where

data Date = native java.util.Date where
    native new :: () -> IO (MutableIO Date)             -- new Date()
    native toString :: Mutable s Date -> ST s String    -- d.toString()

--- 'IO' action to give us the current time as 'String'
current :: IO String
current = do
    d <- Date.new ()  -- reads system timer, hence IO
    d.toString

main args =  
    forever do
        current >>= print   -- print formatted date
        print "\r"          -- followed by carriage return
        stdout.flush        -- make sure it's shown
        Thread.sleep 999L   -- wait 0.999 seconds

Feature	Supported	Token	Example
MultiLine Comments	✓	{- -}	{- A comment -}
Comments	✓		-- A comment
Line Comments	✓	--	-- A comment
Type Inference	✓
Semantic Indentation	X

Frege - Programming language

Language features