Playing With Haskell

My tech book club is starting to look at Haskell. I’m as big of a language addict as anyone so I wanted to dive in early and this is the overview of what I’ve found so far

Statically Typed But Dynamically Inferred

for those of you familiar with Boo this is a familiar concept to you. Once a type is made that type will not autoconvert. For Example:

let i = 6 –this is now going to be an integer

let f = 1.2 –this is now a float

i + f /–will throw exception

Cannot set variable twice

this is from what I understand something that all functional languages share some concept of. (Erlang views the second attempt to set a variable as a “match” request).

x = 10

x = 11

when running the source file results in:

Multiple declarations of `Main.x’

Declared at: functions.hs:1:0


Failed, modules loaded: none.

My Least Favorite Thing In Python AKA Significant Whitespace

In the above code file in my previous example I had an error with an extra whitespace hiding about. I got used to this in Python by using soft tabs and being aware of phantom white space. Not happy about this.

No Loops!

The two primary ways I’ve found to replace loops are recursion and map. Map is a standard of functional languages and pretty easy to grasp. It’s just a way of saying “run a specified function on each item in the list”. A quick example of map is as follows:

doubleList ls = map doubleInt ls — function named “doublelist” with parameter of ls
    where doubleInt x = x*2   –doubles x which represents each value in list

doubled = doubleList [1,2,3,4,5] –set global variable with function applied

At A Glance

Haskell seems to have an easier to learn syntax than Erlang, while still being less ceremonial than other languages I’ve used. I kinda dig the no parenthesis syntax of functions, and of course I don’t miss foreach loops with map.

Finally, I’ll be anxious to find out what the multi-core story is vs Erlang.

Simple BDD/TDD