I'm please to announce HCL 1.0 - a library for building command line interfaces. The library exports a mix of low and high-level functions for building programs which gather simple values, ask yes/no questions, or present hierarchical menus. The library is not intended to do complex, full-screen UIs ala ncurses - it is intended for line-oriented interfaces. Included with the library is a hangman game, so if nothing else you can enjoy that. Where do I get it? ============= Download from Hackage at: http://hackage.haskell.org/cgi-bin/hackage-scripts/package/HCL-1.0 How do I use it it? ============= It's Cabal-ized so, after downloading and unpacking: runghc Setup.hs configure runghc Setup.hs build runghc Setup.hs install Note I had some inconsistent results building with HEAD cabal, but the version distributed with GHC works great (1.1.6.2). To play hangman, execute 'hangman'. Once installed, you can look at it in GHCi by loading the "HCL" module. Tell me more! ========== This library lets you do a lot of cool things. For example, here's a simple guess a number game: guess_num_fun = do target <- reqIO $ getStdRandom (randomR (1::Integer,100)) let guessed val = case compare target val of GT -> do { reqIO $ putStrLn "Too low!"; return False } LT -> do { reqIO $ putStrLn "Too high!"; return False } EQ -> do { reqIO $ putStrLn "You win!"; return True } reqUntil guessed (prompt "Enter a number between 1 and 100: " reqInteger) "reqUntil" takes a predicate and asks for a response until the predicate is true. In the case above, the user is asked to enter an integer. Once they guess the number, the program ends. The library makes it easy to gather structured values. For example, imagine this data structure: data Taxpayer = Taxpayer { name :: String, age :: Int, ssn :: String } deriving (Read, Show) One way to use HCL to get Taxpayer values from the user is to take advantage of its Read instance: reqTaxpayer :: Request Taxpayer reqTaxpayer = prompt "Please enter tax payer information: " (reqRead reqResp) But that is ugly because the user has to type a "Read"-able string:
getTaxpayer reqTaxpayer Please enter tax payer information: Taxpayer {name="John", age = 30, ssn = "" }
However, we can build a form of sorts and make life much easier for the user: reqTaxpayerEasy :: Request Taxpayer reqTaxpayerEasy = do name <- prompt "Please enter the tax payer's name: " reqResp age <- prompt "Please enter their age: " reqInt ssn <- prompt "What is their SSN/ASN: " reqResp return (Taxpayer name age ssn) Which looks like this:
getTaxpayer reqTaxpayerEasy Please enter the tax payer's name: Bob Please enter their age: 50 Please enter their SSN/ASN: 111-11-1111
The library also makes simple hierarchical menus easy to build. The below defines the menu structure for a hypothetical PIM: reqMenu $ reqSubMenu topMenu "Manage contacts" manageContactsMenu $ reqSubMenu topMenu "Manage calendar" (reqMenuItem "Add an event" ... $ ... reqMenuExit "Return to previous menu" reqMenuEnd) $ -- End the menu definition reqMenuEnd -- Defines a partial menu manageContactsMenu = reqMenuItem "Add a contact" ... $ ... reqMenuExit "Return to previous menu" reqMenuEnd These and more examples are distributed with the library in the examples directory. Anything else? =========== Feedback, praise and criticism are welcome. Feedback regarding 'idiomatic' usage is especially desired. This is a first for me so any responses are appreciated. The library was developed on Windows using GHC - please let me know of any odd *nix and Hugs bugs. This library was inspired in part by the Ruby HighLine library (http://highline.rubyforge.org/). Many thanks Mark Jones for his input on HCL's design and implementation.