Ticket #57: vectorNegateShowBugwithUserDefinedDatatypes.hs

-- Author: phil - kaffeepause73@yahoo.de

import qualified Data.Vector.Unboxed as V


-- A. Originally intended code using signal datatype -- create problem with show on negated signal
-- Type synonyms to make things easier to read
type Name = String -- Name
type Time = (V.Vector Double) -- time Vector
type Vect = (V.Vector Double) -- data Vector
type Unit = String -- Unit

-- define datatype nesting vector with other data in a 4-touple
newtype Signal = Signal (Name, Time, Vect, Unit) 

-- functions to access data in 4-touple
getName :: Signal -> String
getName (Signal (n,t,v,u)) = n

getTime :: Signal -> Vect 
getTime (Signal (n,t,v,u)) = t

getVect :: Signal -> Vect
getVect (Signal (n,t,v,u)) = v

getUnit :: Signal -> Unit
getUnit (Signal (n,t,v,u)) = u

-- function to negate signal using smap          
snegate s1 = smap negate s1 "negate"

-- show instance for new datatype signal 
instance Show Signal where  
           show s  = "TimeSignal time: " ++ show (getName s) ++ " val:" ++ show (getVect s) ++ show (getUnit s)    


-- smap only acesses signal data an calls V.map
smap :: (Double -> Double) -> Signal -> String -> Signal
smap f s1 fstr =  Signal (n,t,v,u)
               where 
                 n = getName s1
                 t = getTime s1
                 vdata = getVect s1
                 u = getUnit s1
                 v = V.map f v -- when time data is same

-- B. Alternative negate function directly on V.vector data types to check 
-- # Direct negate funct 
                 
vnegate :: V.Vector Double -> V.Vector Double
vnegate v = V.map negate v


-- ### main to test ways A & B: create different vectors and signals ans checks whether show works fine

main = do          
     -- create a vector
     let v=V.fromList([0..10])

     -- create a negated vector
     let vn = vnegate v    

     -- show bothvectors - works fine :-)
     putStrLn "VectorTests"
     putStrLn (show v)
     putStrLn (show vn)     

     -- create signal with vector
     let s = Signal("name",v,v,"N")

     -- create signal with negated vector
     let sn = Signal("name",vn,vn,"N")

     -- negate original signal s
     let sn2 = snegate s
   
     -- showing these works fine 
     putStrLn "SignalTests"
     putStrLn (show s)
     putStrLn (show sn)

     -- this crashes the program :-(
     putStrLn "uuups"
     putStrLn (show sn2) -- shows <<LOOP>>

     -- this line doesn't appear anymore
     putStrLn (show "test")