[Haskell-beginners] Re: Integer factorization

Heinrich Apfelmus apfelmus at quantentunnel.de
Fri Mar 13 06:29:10 EDT 2009

Francesco Bochicchio wrote:
> Heinrich Apfelmus wrote:
>> Stylistically, one usually uses shorter variable names in Haskell.
> <beginner rant>
> Sometime too short peraphs?  At least, this is one of the things that slows
> down my understanding of code posted
> on this list on or on various haskell tutorial. In any other language I
> know, programmers learn to give meaningful names to variable and functions,
> so when one reads a program, one can use the name to remember what the
> function does. Then one cames to haskell ...
> I guess the short names comes from mathematic background, but  still ...
> haskell is already very succint - even more so
> when you use pointfree programming - and if one also uses names like a,e,i (
> look at Array function definitions ), ...
> </beginner rant>
> Rant apart, I notice that in my own excercises I tend to shorten names, so
> maybe there is a reason for that.
> Nevertheless readability tends to be a big issue in languages used in IT
> industry, and my feeling is that haskell
> tends to err on the laconic side of the balance.

The goal is of course to make code readable, that's why I recommend
short names. :D

Abstraction is the one driving force for very short names. For example,
take the definition of  foldr

   foldr f z []     = z
   foldr f z (x:xs) = f x (foldr f z xs)

Since this function is polymorphic, so f , z  and the  xs  can be
anything, using more "descriptive" variable names is simply not
possible; the key point of fold is its generality.

A second, and my main reason for short names, or rather against long
names, is that names should be to the point. None of the names


accurately describe the object they represent. The primes are not "new",
the prime is not "on top". The "do" is a prefix does not carry a meaning
either, it just conveys that  doFactors  has something to do with
factors . This is best expressed by making  doFactors  a local
definition in the where-block of  factors .

The name  eratosthenesFilter  is ok, but since there is no other
eratosthenes around, no meaning is lost by shortening it to simply
eratosthenes . Not to mention that the conventional term is "sieve", not
"filter". The documentation has to elaborate on it anyway.

The generality of the name  num  hints that a single letter name is

The names that I think are great because they are to the point are


> Out of curiosity, there is any reason why you called the auxiliary function
> 'go' ?

Convention. Often, an auxiliary function that does basically the same
thing as the main function  factors  but with an extra parameter will be
named  factors' . The apostrophe has the drawback that it's easy to
forget, so some people now name such auxiliary functions  go  instead.



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