ModulesNotRecords

root edited this page Oct 11, 2017 · 5 revisions

In facts before deciding between Records and Modules, consider the following:

  • Will you need to build a structure of this "type" "à la volée"
    • If so, a Record is probably better as you can't do inside terms a "let m := [module] in [expr]"
  • Do you want something very modular; for instance given three module types A, B and C, and two functors, f: A -> B and g: B -> C, be able to define the functor h: A -> C, by h=*g*o*f*?
    • If so, Records are more ... modular than ... modules...
  • Will your structure be extracted or do you want it extractable to caml/Haskell/...?
    • If so, I don't recommend use of Record (except maybe if you can express it directly with a record in the target language)
  • Will you need to define useful tactics inside your module?
    • If so you won't be able to define them inside Records, and lose the "dot" notation.
  • Will you need some toplevel instructions, such as "Implicit Arguments", "Print" and so...
    • Use Modules (Note that for Notations, you have a way to use "Reserved Notation" and "where" for Records)
  • Will you need some performances?
    • Use Modules, all is defined at toplevel and won't require function calls

In all other cases, Records are often a better solution.

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