Begginer question

  Hi,

  When compiling this:

************
import Complex;

complex_root :: (Float, Float, Float) -> (Complex Float, Complex Float)
complex_root (a,b,c) = (x1,x2) where {  
        delta = b * b - 4 * a * c :: Float;
	sqr_delta = if delta >= 0 then (sqrt delta) :+ 0 else 0 :+ (sqrt delta) 
:: (Complex Float);
        x1 = (b + sqr_delta)/(2 * a);
        x2 = (b - sqr_delta)/(2 * a);
}
***********

  I get this error message:

**********
Couldn't match `Float' against `Complex Float'
        Expected type: Float
        Inferred type: Complex Float
    In the second argument of `(+)', namely `sqr_delta'
    In the definition of `x1': x1 = (b + sqr_delta)
***********

  Can you help me finding what is wrong? Shouldn't "b" be converted to 
Complex Float and be summed to sqr_delta?

  Thanks for your help,
  Maurício