[Haskell-beginners] Most important Functional Methods

[Patrick Mylund Nielsen]

On Sat, Jun 7, 2014 at 8:40 AM, Erik Price <erikprice at gmail.com> wrote:

>
>
> On Saturday, June 7, 2014, Richard Seldon <arcseldon at gmail.com> wrote:
>
>> Hello,
>>
>> I have a general question, not specific to Haskell although I am learning
>> Haskell as I ask this question..
>>
>> Please can someone provide consensus on the most important functional
>> methods in their view.
>>
>> I read somewhere that having map, reduce, filter, mergeAll, and zip
>> pretty much means everything else can be derived.
>
>
> You might be interested in reading this excellent introductory article on
> folds, which are Haskell's equivalent to what some languages call reduce:
>
> http://www.cs.nott.ac.uk/~gmh/fold.pdf
>
> It shows how many of the basic higher-order functions (such as map,
> filter, etc) can be derived from a fold.
>
> e
>

In fact, concatMap (flatMap) is defined like so:

-- | Map a function over a list and concatenate the results.concatMap
             :: (a -> [b]) -> [a] -> [b]concatMap f             =
foldr ((++) . f) []
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