[Haskell-beginners] a problem with maps

[Ertugrul Soeylemez]

David Place <d at vidplace.com> wrote:

> > Point taken, but to get serious with Haskell you will want to learn
> > applicative functors and at least the function arrow anyway.
>
> Interesting thoughts, Ertugrul.  I would argue that you can get very
> serious with Haskell without understanding applicative functors and
> the function arrow.  The very basic aspects of the language (the type
> system, higher-order functions, lazy evaluation, etc…) are already so
> powerful, that you really don't need to add complexity to simple
> programs by including some of the more obscure extensions.  I could
> see if it made the code substantially more compact.  In this case, it
> makes the code more verbose as you need to import the two modules to
> do something which can be so trivially expressed as an abstraction.

Haskell application development is more than just the language.  The
language itself is very powerful, yes, but serious applications I write
usually have quite a few dependencies.  If you want to reinvent the
wheel for everything, then yes, I'm exaggerating.  Personally I don't
want to, because there are great libraries and design patterns out
there, for which you simply need to understand more than just the
language.

It's as simple as this:  To get serious with Haskell, you need to
understand Haskell monads.  Understanding them implies understanding
applicative functors (not necessarily the applicative style).  For many
of the useful libraries you will want to go further and understand monad
transformers and more.

I'm not talking about any ideals here.  I'm talking about real world
application development, which is what I am doing.


> When you write a program, do you think of it as a document only for
> the compiler to understand, or might some other people need to
> understand it someday?

"It"?  For me type signatures are specification for the compiler and
documentation for humans, along with Haddock-style comments.  My code is
usually very well documented.  In most cases Haddock shows me a coverage
of 100% for all of my source files, and every top-level and
'where'-definition has a type signature.  I'm very rigorous here.

All of the power I get from Haskell itself, the base library and the
many libraries I use I view as tools to get stuff done quickly, safely
and elegantly.  As said, there is always a simpler way to write stuff,
but I have a certain style, which I follow consistently, and in that
style I write 'second pure'.  That's it.

Why not '(:[])'?  Simply because I hate it and find it confusing.  Why
not 'return'?  Because I write my code reasonably general.  Not that
using 'return' would change the type signature in question, but it is
just my style.  In a do-block I use 'return'.  Everywhere else I use
'pure'.  Consistently.  Why 'second'?  Because it's convenient.


Greets,
Ertugrul


-- 
nightmare = unsafePerformIO (getWrongWife >>= sex)
http://ertes.de/