Another Confusing Haskell Error Message

The Error Message I’ve written before about just how befuddling Haskell error messages can be, especially for beginners. And now, even though I have some professional Haskell development under my belt, I ran across a Haskell error message that confused me for a bit, where I had to get help. It’s clear to me now when I look at the error message what it’s trying to say, but I legitimately was stumped by it, and so, even though it’s embarrassing for me now, I feel the need to write about how this error message could have been easier to understand:

Haskell Error Messages: Come on!

I am a big fan of strongly typed languages, and my favorite GC’d language is Haskell. And I want you, the reader, to keep that in mind today. What I am writing is some commentary about a language I deeply love, some loving criticism. So here’s what happened: A few days ago, I was showing off some Haskell for a friend who primarily programs in Python. The stakes were high – could I demonstrate that this strange language was worth some investigation?

The Haskeller’s Hungarian Notation

When I was first learning to program, a long time ago, it was in BASIC, and you had to annotate your variable names to indicate what type something is. foo would be a number, whereas foo$ would be a string. This meant that there could only be as many types of information as there were symbols to put after your variable, but that was okay for the sort of programming BASIC was used for.