Haskell Maybe type -> type -

i running problem :

couldn't match expected type ‘int’ actual type ‘maybe int’ 

can somehow convert ‘maybe int’ ‘int’??

if index == nothing                   let index = 0        putstrln(fancyprint2 $ kaasasolevlist !! index)    else               let index = index        putstrln(fancyprint2 $ kaasasolevlist !! index) 

i tried this, gives me :

exception: <<loop>> 

you have several different options around this

first using if statement, small modification (avoid doing though)

if index == nothing                   let index' = 0        putstrln $ fancyprint2 $ kaasasolevlist !! index'    else               let (just index') = index        putstrln $ fancyprint2 $ kaasasolevlist !! index' 

i'm writing index' here, because haskell doesn't allow overwrite existing variables, let hide them. it's better practice label "modified" versions of variable "prime" symbol (') @ end. way can access original if need be.

second can use case expression turns code into

case index of    -> putstrln $ fancyprint2 $ kaasasolevlist !!   nothing -> putstrln $ fancyprint2 $ kaasasolevlist !! 0 

or if clean bit using where clause:

case index of    -> putindex   nothing -> putindex 0 putindex x = putstrln $ fancyprint2 $ kaasasolevlist !! x 

lastly there's frommaybe lets this:

import data.maybe (frommaybe)  -- ...    let index' = frommaybe 0 index   putstrln $ fancyprint2 $ kaasasolevlist !! index' 

you can use guards. seeing don't know code-snippet comes from, don't know if it's reasonable use guards.

you can read more guards, case expressions , pattern matching here