> let a1 = 2 :: Int
> let a2 = 3 :: Int
> a1 * a2
6
> let b1 = 2 :: Double
> let b2 = 3 :: Double
> b1 * b2
6.0
> a1 * b2
<interactive>:1387:6: error:
• Couldn't match expected type ‘Int’ with actual type ‘Double’
• In the second argument of ‘(*)’, namely ‘b2’
In the expression: a1 * b2
In an equation for ‘it’: it = a1 * b2
> a2 * b1
<interactive>:1388:6: error:
• Couldn't match expected type ‘Int’ with actual type ‘Double’
• In the second argument of ‘(*)’, namely ‘b1’
In the expression: a2 * b1
In an equation for ‘it’: it = a2 * b1
>