[Haskell-cafe] [newbie question] Memoization automatic in Haskell?

Jonathan Cast jonathanccast at fastmail.fm
Sat Jan 12 18:21:25 EST 2008

On 12 Jan 2008, at 3:16 PM, Hugh Perkins wrote:

> On Jan 12, 2008 10:54 PM, Henning Thielemann
> <lemming at henning-thielemann.de> wrote:
>> On Sat, 12 Jan 2008, Hugh Perkins wrote:
>>> I guess that Haskell's referential transparence means the answers to
>>> the isPerfectSquare will be cached, ie automatically memoized? (not
>>> sure if is correct term?)
>> http://www.haskell.org/haskellwiki/Memoization
> Interesting... but I dont understand... I thought that referential
> transparence meant that once the answer to a function has been
> calculated once, it will always be the same,


> and that the interpreter
> can,


> and will,

Caching is not infrequently a terrible implementation strategy, for  
space reasons (and sometimes for time reasons as well).  Deciding  
whether to use it is a delicate engineering tradeoff, and, while the  
compiler will do its best, the starting point is decided by the  
programmer.  Lists get cached by default; functions over integers do  
not.  The compiler may change that decision, but it will make sure to  
nail down in triplicate that doing so is an improvement for every  
program subject to the optimization first, which means it probably  

> cache this answer?


More information about the Haskell-Cafe mailing list