Commit b69525df authored by Robbert Krebbers's avatar Robbert Krebbers

Write some documentation about the new `iAlways` tactic.

parent 6dc83bcb
......@@ -68,6 +68,22 @@ Arguments IntoPersistent {_} _ _%I _%I : simpl never.
Arguments into_persistent {_} _ _%I _%I {_}.
Hint Mode IntoPersistent + + ! - : typeclass_instances.
(* The `iAlways` tactic is not tied to `persistently` and `affinely`, but can be
instantiated with a variety of comonadic (always-style) modalities.
In order to plug in an always-style modality, one has to decide for both the
persistent and spatial what action should be performed upon introducing the
modality:
- Introduction is only allowed when the context is empty.
- Introduction is only allowed when all hypotheses satisfy some predicate
`C : PROP → Prop` (where `C` should be a type class).
- Introduction will only keep the hypotheses that satisfy some predicate
`C : PROP → Prop` (where `C` should be a type class).
- Introduction will clear the context.
- Introduction will keep the context as-if.
Formally, these actions correspond to the following inductive type: *)
Inductive always_intro_spec (PROP : bi) :=
| AIEnvIsEmpty
| AIEnvForall (C : PROP Prop)
......@@ -80,6 +96,8 @@ Arguments AIEnvFilter {_} _.
Arguments AIEnvClear {_}.
Arguments AIEnvId {_}.
(* An always-style modality is then a record packing together the modality with
the laws it should satisfy to justify the given actions for both contexts: *)
Record always_modality_mixin {PROP : bi} (M : PROP PROP)
(pspec sspec : always_intro_spec PROP) := {
always_modality_mixin_persistent :
......
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