2009/3/11 Mark Spezzano
Hi,
I’m very familiar with the concept of Design Patterns for OOP in Java and C++. They’re basically a way of fitting components of a program so that objects/classes fit together nicely like Lego blocks and it’s useful because it also provides a common “language” to talk about concepts, like Abstract Factory, or an Observer to other programmers. In this way one programmer can instantly get a feel what another programmer is talking about even though the concepts are fundamentally abstract.
Because Haskell is not OO, it is functional, I was wondering if there is some kind of analogous “design pattern”/”template” type concept that describe commonly used functions that can be “factored out” in a general sense to provide the same kind of usefulness that Design Patterns do for OOP. Basically I’m asking if there are any kinds of “common denominator” function compositions that are used again and again to solve problems. If so, what are they called?
Hi, A particular instance of what can replace the idea of design pattern is given by this now famous post : http://blog.sigfpe.com/2009/01/haskell-monoids-and-their-uses.html You'll see that what 'speaks' to the haskell programmers, maybe in the same way you say design patterns speak to another oo programmer, is much more fitted to the language in haskell. At a lower scale, the reusability of some simple functions like fold or map is reflected at a higher scale by the reusability of concepts like monoids (whih 'exist' in the language, as type classes, while a pattern doesn't). Cheers, Thu