On Wednesday, October 5, 2016 at 4:24:01 PM UTC+5:30, BartC wrote: > On 05/10/2016 11:03, Ben Bacarisse wrote: > > Gregory Ewing writes: > > > >> Steve D'Aprano wrote: > >> > >>> And (shamelessly using Python syntax) if I have a function: > >>> > >>> def spam(x): > >>> print(x) > >>> print(x+1) > >>> > >>> spam(time.sleep(60) or 1) > >> > >> You can't write that in Haskell, because Haskell's > >> equivalent of print() is not a function (or at least > >> it's not a function that ever returns), and neither > >> is sleep(). > > > > I suppose it all depends on what "that" is exactly. Here is the closest > > match I could come up with: > > > > import Control.Concurrent > > > > spam io = do x <- io; > > print x; > > print (x+1) > > > > main = spam (do threadDelay (2*10^6); return 1) > > > > It matches the Python in that the delay happens once. To get the > > behaviour being hinted at (two delays) you need to re-bind the IO > > action: > > > > spam io = do x <- io; > > print x; > > x <- io; > > print (x+1) > > (I downloaded Haskell (ghc) yesterday to try this out. First problem was > that I couldn't figure out how to do two things one after another > (apparently you need 'do'). > > And when I tried to use a random number function in an expression to see > if it was evaluated once or twice, apparently my installation doesn't > have any form of random() (despite being a monstrous 1700MB with 20,000 > files).
In general this may be true. In general you need to use cabal or stack in haskell-world like you use pip in python world to get what stuff you need However for Random it seems to be part of System: https://hackage.haskell.org/package/random-1.1/docs/System-Random.html Here’s a session just blindly following https://www.schoolofhaskell.com/school/starting-with-haskell/libraries-and-frameworks/randoms $ ghci GHCi, version 7.10.3: http://www.haskell.org/ghc/ :? for help Prelude> import System.Random Prelude System.Random> import Control.Monad (replicateM) Prelude System.Random Control.Monad> let main = replicateM 10 (randomIO :: IO Float) >>= print Prelude System.Random Control.Monad> main [0.57468385,0.84545535,0.1624645,0.8491243,0.48347688,2.9622138e-2,0.70125,0.9189069,0.5903369,0.26639372] Small modif from the link above: I changed main = replicateM... to let main = replicateM... for reasons quite related to this whole long thread! viz. = ie definitions goes into haskell files At the repl one can only write expressions let wangles around that > > Not an easy language..) I am not going to argue that! Every language (that Ive ever used) has oddities that tripped me up. Once these initial hurdles are crossed is it hard or easy is a real but different question. -- https://mail.python.org/mailman/listinfo/python-list
