On 11/5/07, Levi Stephen
Hi,
I'm was wondering how most people work during when designing a functional program. Do you create data structures/types first? Do you work from some type signatures?
For example, take a blog. Is the first step likely to be something like:
data BlogEntry = BlogEntry { title::String,content::String,comments::[Comment] } type Blog = [BlogEntry]
or more likely thinking about what functions will be required:
addEntry :: BlogEntry -> Blog -> Blog displayBlog :: Blog -> HTML displayEntry :: BlogEntry -> HTML
I don't know how you can do one without the other. I would probably start in a case like this by writing down a few basic types, then trying to start to write down the function type signatures, which will probably point to more types that need to be defined, iterating until I reach a fixed point. I can't write type signatures unless I know what the types are. But I don't know what the types should look like unless I know what the interface should look like, either. One thing that's for sure, though -- I always write type signatures for top-level definitions. I can't think straight unless I write the type signature before writing the code. Cheers, Tim -- Tim Chevalier * catamorphism.org * Often in error, never in doubt "Thus spake the Master Programmer: When you have learned to snatch the error code from the trap frame, it will be time for you to leave."--J. Geoffrey