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I'm very new to haskell.

How can I return (x1,x2) and print it out from my code?

qqq x
   | x < 0  x1 = mod (-x) 10 
   | 1 < x && x < 99 x1 = mod x 10
   | x2 = mod x 10

CodePudding user response：

You are using guards the wrong way. You seem to see these as if statements, that you then can use for assignements. In Haskell, you do not assign values to a variable, you declare these. You can work with:

qqq :: Integral a => a -> (a, a)
qqq x
   | x < 0 = (mod (-x) 10, x2)
   | 1 < x && x < 99 = (mod x 10, x2)
  where x2 = mod x 10

Here each guard thus has a condition before the equation sign (=), and at the right side returns a 2-tuple with as first item an expression for x1, and as second item x2.

You should also implement extra case(s) for x == 1 and x >= 99, these are not covered by the two guards.