Issue with Haskell's "do"

Question

I wrote a Haskell function that calculates the factorial of every number in a given list and prints it to the screen. ``` factPrint list = if null list then putStrLn "" else do putStrLn ((show.fact.head) list) factPrint (tail list) ``` The function works, but I find the third line a bit confusing. Why hasn't the compiler(GHC) reported an error on it since there is no "do" before the "putStrLn" (quasi?)function? If I omit "do" from the 4th line, an error pops up as expected. I'm quite new to Haskell and its ways, so please pardon me if I said something overly silly.

Accepted Answer

```
do putStrLn ((show.fact.head) list)
   factPrint (tail list)
```

is actually another way of writing

```
putStrLn ((show.fact.head) list) >> factPrint (tail list)
```

which, in turn, means

```
putStrLn ((show.fact.head) list) >>= \_ -> factPrint (tail list)
```

The `do` notation is a convenient way of stringing these monads together, without this other ugly syntax.

If you only have one statement inside the `do`, then you are not stringing anything together, and the `do` is redundant.

Issue with Haskell's "do"

Solution

Problem