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- The earlier proof-of-concept file NPeano (which instantiates
the "Numbers" framework for nat) becomes now the entry point
in the Arith lib, and gets renamed PeanoNat. It still provides
an inner module "Nat" which sums up everything about type nat
(functions, predicates and properties of them).
This inner module Nat is usable as soon as you Require Import Arith,
or just Arith_base, or simply PeanoNat.
- Definitions of operations over type nat are now grouped in a new
file Init/Nat.v. This file is meant to be used without "Import",
hence providing for instance Nat.add or Nat.sqrt as soon as coqtop
starts (but no proofs about them).
- The definitions that used to be in Init/Peano.v (pred, plus, minus, mult)
are now compatibility notations (for Nat.pred, Nat.add, Nat.sub, Nat.mul
where here Nat is Init/Nat.v).
- This Coq.Init.Nat module (with only pure definitions) is Include'd
in the aforementioned Coq.Arith.PeanoNat.Nat. You might see Init.Nat
sometimes instead of just Nat (for instance when doing "Print plus").
Normally it should be ok to just ignore these "Init" since
Init.Nat is included in the full PeanoNat.Nat. I'm investigating if
it's possible to get rid of these "Init" prefixes.
- Concerning predicates, orders le and lt are still defined in Init/Peano.v,
with their notations "<=" and "<". Properties in PeanoNat.Nat directly
refer to these predicates in Peano. For instantation reasons, PeanoNat.Nat
also contains a Nat.le and Nat.lt (defined via "Definition le := Peano.le",
we cannot yet include an Inductive to implement a Parameter), but these
aliased predicates won't probably be very convenient to use.
- Technical remark: I've split the previous property functor NProp in
two parts (NBasicProp and NExtraProp), it helps a lot for building
PeanoNat.Nat incrementally. Roughly speaking, we have the following schema:
Module Nat.
Include Coq.Init.Nat. (* definition of operations : add ... sqrt ... *)
... (** proofs of specifications for basic ops such as + * - *)
Include NBasicProp. (** generic properties of these basic ops *)
... (** proofs of specifications for advanced ops (pow sqrt log2...)
that may rely on proofs for + * - *)
Include NExtraProp. (** all remaining properties *)
End Nat.
- All other files in directory Arith are now taking advantage of PeanoNat :
they are now filled with compatibility notations (when earlier lemmas
have exact counterpart in the Nat module) or lemmas with one-line proofs
based on the Nat module. All hints for database "arith" remain declared
in these old-style file (such as Plus.v, Lt.v, etc). All the old-style
files are still Require'd (or not) by Arith.v, just as before.
- Compatibility should be almost complete. For instance in the stdlib,
the only adaptations were due to .ml code referring to some Coq constant
name such as Coq.Init.Peano.pred, which doesn't live well with the
new compatibility notations.
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Pierre Letouzey
letouzey