Question: I have a list of strings (see below) how do I concatenate these strings into one list containing one string.

```
["hello","stack","overflow"] 

```

to 

```
["hellostackoverflow"]

```

I am just allowed to import Data.Char and Data.List

Answer: 
```hs
concat ["hello","stack","overflow"] -- => "hellostackoverflow"

```
You can also use the list monad to reduce the list to a single string, then re-wrap the result in a list.

```
> [["hello", "stack", "overflow"] >>= id]
["hellostackoverflow"]

```

The preceding avoids explicitly use of `Control.Monad.join`:

```
> import Control.Monad
> [join ["hello", "stack", "overflow"]
["hellostackoverflow"]

```