A Builder is an efficient way to build lazy Text values. There are several functions for constructing builders, but only one to inspect them: to extract any data, you have to turn them into lazy Text values using toLazyText.
Internally, a builder constructs a lazy Text by filling arrays piece by piece. As each buffer is filled, it is 'popped' off, to become a new chunk of the resulting lazy Text. All this is hidden from the user of the Builder.
Efficient construction of lazy Text values. The principal operations on a Builder are singleton, fromText, and fromLazyText, which construct new builders, and mappend, which concatenates two builders.
To get maximum performance when building lazy Text values using a builder, associate mappend calls to the right. For example, prefer
> singleton 'a' `mappend` (singleton 'b' `mappend` singleton 'c')
> singleton 'a' `mappend` singleton 'b' `mappend` singleton 'c'
as the latter associates mappend to the left.