Merge branch 'msammler/select_tac' into 'master'

Added select and select_revert tactics

See merge request iris/stdpp!142

CHANGELOG.md

@@ -3,6 +3,8 @@ API-breaking change is listed.
 
 ## std++ master
 
+- Added the `select` and `revert select` tactics for selecting and
+  reverting a hypothesis based on a pattern.
 - Extracted `list_numbers.v` from `list.v` and `numbers.v` for
   functions, which operate on lists of numbers (`seq`, `seqZ`,
   `sum_list(_with)` and `max_list(_with)`). `list_numbers.v` is

theories/tactics.v

@@ -520,6 +520,25 @@ Ltac find_pat pat tac :=
       tryif tac x then idtac else fail 2
   end.
 
+
+(** [select] finds the first hypothesis matching [pat] and passes it
+to the continuation [tac]. Its main advantage over using [match goal
+with ] directly is that it is shorter. If [pat] matches multiple
+hypotheses, then [tac] will only be called on the first matching
+hypothesis. If [tac] fails, [select] will not backtrack on subsequent
+matching hypotheses.
+
+[select] is written in CPS and does not return the name of the
+hypothesis due to limitations in the Ltac1 tactic runtime (see
+https://gitter.im/coq/coq?at=5e96c82f85b01628f04bbb89). *)
+Tactic Notation "select" open_constr(pat) tactic(tac) :=
+  lazymatch goal with
+  (* The [unify] is necessary, otherwise holes in [pat] stay as side-conditions *)
+  | H : pat |- _ => let T := (type of H) in unify T pat; tac H
+  end.
+(** [select_revert] reverts the first hypothesis matching [pat]. *)
+Tactic Notation "revert" "select" open_constr(pat) := select pat (fun H => revert H).
+
 (** Coq's [firstorder] tactic fails or loops on rather small goals already. In
 particular, on those generated by the tactic [unfold_elem_ofs] which is used
 to solve propositions on sets. The [naive_solver] tactic implements an