Notebook: datatypes

[yallop]

• Defining datatypes
  • Very simple records and variants.
  • We won't need to define parameterised or recursive types (but those concepts will be needed to understand list)
• Lists
• Options
  • we should say that option isn't special (i.e. it's not OCaml's equivalent of null, which is sui generis)
• Constructing values
• Pattern matching
  • Using match should be sufficient: no need for destructuring let or for function
  • match for records, variants, options and lists
  • some deep pattern matching
  • when guards
  • nested match: need to parenthesize the inner match

[yallop]

Description fleshed out a bit.

[lpw25]

Forgot to read this before writing the first draft. The main thing I'm missing is Lists, which I do not talk about as a variant type. This is partly because they have specialised syntax, and partly because I already used them in the "basics" notebook. At the very least, I should add a sub-section on pattern matching lists.

I'm also missing a sub-section on when guards.

[yallop]

Fixed by #12.