[Haskell-beginners] help with IO guards
miroslav.karpis at gmail.com
Thu Jan 15 11:51:37 UTC 2015
please is there a way to have guards with 'where' that communicates with
IO? Or is there some other more elegant way? I can do this with classic
if/else,...but I just find it nicer with guards.
I have something like this (just an example):
f :: Int -> IO String
| null dbOutput = return "no db record"
| otherwise = return "we got some db records"
where dbOutput = getDBRecord x
getDBRecord :: Int -> IO [Int]
getDBRecord recordId = do
putStrLn $ "checking dbRecord" ++ show recordId
--getting data from DB
problem is that db dbOutput is IO and the guard check does not like it:
Couldn't match expected type ‘[a0]’ with actual type ‘IO [Int]’
In the first argument of ‘null’, namely ‘dbOutput’
In the expression: null dbOutput
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