Question: Given an example array of `[-7, 8, -3, 4, -2, -7, 7]`, find the highest product that any of three of those numbers may yield.

Related question for solution of the same problem in Python, that did not get an answer with code: [**Finding highest product of three numbers**](https://stackoverflow.com/questions/29710357/finding-highest-product-of-three-numbers).

For the example array provided in the first paragraph, expected result is `392`.

Answer: 
Should be

```
module Main where

```

or

```
module Main (main) where

```
This answer for specifically for reader of [Real World Haskell](http://book.realworldhaskell.org). It seems that the book uses an older version of Haskell where `main` need not be explicitly mentioned in the list of exports. In the latest version, this is no longer the case. 

There are two aspects that need to be mentioned:

* you need to write `module Main (main) where` so that `main` is exported
* you do not need to make an object file of `SimpleJSON.hs` and mention it while compiling `Main.hs` i.e simply running `ghc -o simple Main.hs` will suffice

As a general note, a couple of reviews on the [Amazon page for the book](https://www.amazon.in/Real-World-Haskell-Bryan-%E2%80%B2sullivan/dp/0596514980/ref=sr_1_2?keywords=real+world+haskell&qid=1570297306&sr=8-2) mention that some aspects covered in the book are out of date. So, if you are following this book, make it a point to use another source to catch up on the differences.