On Sat, Mar 03, 2007 at 08:38:57AM -0600, John Goerzen wrote:
I'm pleased to announce HSH 1.2.0. Since version 1.0.0 was announced a few days ago, there have been some improvements:
How about -||- as an alias for something like `catch` $ \_ -> ? Or I'm not sure the best design, in the sense of how you want to treat booleans. e.g. This would allow simple shell-like error handling in pipes, using exception-throwing as pipes: sh: echo "hello world" | grep z || echo "there is no z" hsh: run $ echo "hello world" -|- "grep z" -||- echo "there is no z" I find this sort of idiom helpful in shell scripting. The catch is that you would probably have to treat the return code of grep as an exception, which often isn't what you want. And, of course, this wouldn't work at all with your haskell grep, unless you change it to throw an exception on failure to match (which seems ugly). Another suggestion: might it be possible to move ShellCommand somehow more directly into the IO monad? It'd be really nice if we wouldn't need the "run $" on every line of a hsh script, and it seems like if you made something like (and I don't believe it could be this simple) (-|-) :: (ShellCommand a, ShellCommand b, RunResult c) => a -> b -> c and then created an instance of ShellCommand for a RunResult, maybe you would only need run when there's no pipe going on? i.e. I'd like to be able to see do l <- "echo hello world" -|- length rnd <- "cat /dev/urandom" -|- take l run $ "echo " ++ (concatMap tohex rnd) where tohex _ = "hex" Yes, this code is stupid and could be simplified, but hopefully you can see what I'd like: to be able to mingle your hsh ShellCommands right into the IO monad. I'm afraid that to work properly, this might require defaulting on the ShellCommand or RunResult classes. If so, it might be a good example to guide the Haskell' discussion of defaulting. I intentionally wrote the above example so the typechecker could determine the result of each line, because I use them... except for the last, which it'll bomb on, and currently needs to be written as runIO. But defaulting would be far cleaner... -- David Roundy http://www.darcs.net