You must have also noticed how the Haskell source code is formatted. The blocks are indented by white spaces. There is no hard and fast rule for indenting; however, it must be noted that there has to be a significant white space indent for a source code block, such as the let clause or the where clause. A simple guideline is that any block should be indented in such a way that it is left aligned and increases the readability of the code. A good Haskell source is easy to read.