Re: [Haskell-beginners] how to check the format of a string ?

22 Feb 2015

      Frerich Raabe schreef op 22-2-2015 om 20:38:
...
On 2015-02-22 19:50, Roelof Wobben wrote:
...
Now im facing this problem.
There is a log file of strings.
Most of them are of this format   char  Number [chars]
What is the best way to check if the string has this format ?
For this particular format I'd go for plain pattern matching and 
guards. Something like
import Data.Char (isLetter, isDigit)
isValid :: String -> Bool
  isValid s = go (words s)
    where
      go ([a]:b:_) = isLetter a && all isDigit b
      go _         = False
This will accept lines starting with a letter followed by some number 
and then (optionally!) some more text.
Thanks,

I can also check if a is equal to I , W or E.

And in the main function check if A =  I/W/E

Roelof