[Haskell-cafe] Command line prompt templates

Donald Bruce Stewart dons at cse.unsw.edu.au
Thu Nov 23 21:03:03 EST 2006

> I was trying to write my own equivalent to Don Stewart's mkcabal but
> ended up getting sidetracked. I made some generalised prompts for use at
> the command line and wanted to get some feedback on them.
> The full code can be found at [1] but the basic summary is like this:
> > prompt :: String -> IO String
> Simple prompt - supply a question and receive the user's answer.
> > promptYesNo :: String -> Maybe String -> IO Bool
> A yes/no question, with an optional value to ask about. I suppose this
> could be simplified to just one string.
> > promptList :: String -> [String] -> Maybe Integer -> IO Integer
> Ask the user to choose from a list, where the result is the number
> chosen. The optional value is a default if the user doesn't pick a
> number.
> > promptListEdit :: String -> [String] -> Maybe Integer -> IO String
> As above, but the last option in the list is an invitation to provide
> your own answer. Again the optional value is the default choice if
> nothing else is chosen. The result here is necessarily the string rather
> than the integer cos I didn't want to complicate matters further with
> stuff like Either types.
> If you can see any flaws or have any suggestions please let me know!

Looks pretty good, though you use 

    case x :: Bool of
        True  -> ...
        False -> ...

    if x then ... else ...

would be preferred.

I wonder if there's a prompt API out there for python or something you
could use for inspiration?

-- Don

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