Merge branch 'hsv/using_lists_droplast'

* hsv/using_lists_droplast:
  lib/mnesia/test/ - Replace reverse(tl(reverse(L))) with lists:droplast/1
  lib/ssh - Replace reverse(tl(reverse(L))) with lists:droplast/1
  lib/wx - Replace reverse(tl(reverse(L))) with lists:droplast/1
  Use lists:droplast/1 in orber/orber_interceptors.erl
  Import and use lists:droplast/1 in v3_core/v3_kernel

OTP-11678
OTP-11677

6 files changed, 17 insertions, 44 deletions

diff --git a/lib/compiler/src/v3_core.erl b/lib/compiler/src/v3_core.erl
index 59863f52ec..291443f824 100644
--- a/lib/compiler/src/v3_core.erl
+++ b/lib/compiler/src/v3_core.erl
@@ -74,7 +74,7 @@
 -export([module/2,format_error/1]).
 
 -import(lists, [reverse/1,reverse/2,map/2,member/2,foldl/3,foldr/3,mapfoldl/3,
-		splitwith/2,keyfind/3,sort/1,foreach/2]).
+		splitwith/2,keyfind/3,sort/1,foreach/2,droplast/1,last/1]).
 -import(ordsets, [add_element/2,del_element/2,is_element/2,
 		  union/1,union/2,intersection/2,subtract/2]).
 -import(cerl, [ann_c_cons/3,ann_c_cons_skel/3,ann_c_tuple/2,c_tuple/1]).
@@ -226,13 +226,13 @@ guard(Gs0, St0) ->
 			Gt1 = guard_tests(Gt0),
 			L = element(2, Gt1),
 			{op,L,'or',Gt1,Rhs}
-		end, guard_tests(last(Gs0)), first(Gs0)),
+		end, guard_tests(last(Gs0)), droplast(Gs0)),
     {Gs,St} = gexpr_top(Gs1, St0#core{in_guard=true}),
     {Gs,St#core{in_guard=false}}.
     
 guard_tests(Gs) ->
     L = element(2, hd(Gs)),
-    {protect,L,foldr(fun (G, Rhs) -> {op,L,'and',G,Rhs} end, last(Gs), first(Gs))}.
+    {protect,L,foldr(fun (G, Rhs) -> {op,L,'and',G,Rhs} end, last(Gs), droplast(Gs))}.
 
 %% gexpr_top(Expr, State) -> {Cexpr,State}.
 %%  Generate an internal core expression of a guard test.  Explicitly
@@ -513,7 +513,7 @@ expr({bin,L,Es0}, St0) ->
     end;
 expr({block,_,Es0}, St0) ->
     %% Inline the block directly.
-    {Es1,St1} = exprs(first(Es0), St0),
+    {Es1,St1} = exprs(droplast(Es0), St0),
     {E1,Eps,St2} = expr(last(Es0), St1),
     {E1,Es1 ++ Eps,St2};
 expr({'if',L,Cs0}, St0) ->
@@ -1588,15 +1588,6 @@ pat_alias_list(_, _) -> throw(nomatch).
 
 pattern_list(Ps, St) -> [pattern(P, St) || P <- Ps].
 
-%% first([A]) -> [A].
-%% last([A]) -> A.
-
-first([_]) -> [];
-first([H|T]) -> [H|first(T)].
-
-last([L]) -> L;
-last([_|T]) -> last(T).
-
 %% make_vars([Name]) -> [{Var,Name}].
 
 make_vars(Vs) -> [ #c_var{name=V} || V <- Vs ].
@@ -1679,13 +1670,13 @@ uclause(#iclause{anno=Anno,pats=Ps0,guard=G0,body=B0}, Pks, Ks0, St0) ->
 uguard([], [], _, St) -> {[],St};
 uguard(Pg, [], Ks, St) ->
     %% No guard, so fold together equality tests.
-    uguard(first(Pg), [last(Pg)], Ks, St);
+    uguard(droplast(Pg), [last(Pg)], Ks, St);
 uguard(Pg, Gs0, Ks, St0) ->
     %% Gs0 must contain at least one element here.
     {Gs3,St5} = foldr(fun (T, {Gs1,St1}) ->
 			      {L,St2} = new_var(St1),
 			      {R,St3} = new_var(St2),
-			      {[#iset{var=L,arg=T}] ++ first(Gs1) ++
+			      {[#iset{var=L,arg=T}] ++ droplast(Gs1) ++
 			       [#iset{var=R,arg=last(Gs1)},
 				#icall{anno=#a{}, %Must have an #a{}
 				       module=#c_literal{val=erlang},
diff --git a/lib/compiler/src/v3_kernel.erl b/lib/compiler/src/v3_kernel.erl
index 9a2b1605ad..6c8089e61d 100644
--- a/lib/compiler/src/v3_kernel.erl
+++ b/lib/compiler/src/v3_kernel.erl
@@ -81,7 +81,7 @@
 -export([module/2,format_error/1]).
 
 -import(lists, [map/2,foldl/3,foldr/3,mapfoldl/3,splitwith/2,member/2,
-		keymember/3,keyfind/3,partition/2]).
+		keymember/3,keyfind/3,partition/2,droplast/1,last/1]).
 -import(ordsets, [add_element/2,del_element/2,union/2,union/1,subtract/2]).
 -import(cerl, [c_tuple/1]).
 
@@ -351,7 +351,7 @@ expr(#c_case{arg=Ca,clauses=Ccs}, Sub, St0) ->
     {Kvs,Pv,St2} = match_vars(Ka, St1),		%Must have variables here!
     {Km,St3} = kmatch(Kvs, Ccs, Sub, St2),
     Match = flatten_seq(build_match(Kvs, Km)),
-    {last(Match),Pa ++ Pv ++ first(Match),St3};
+    {last(Match),Pa ++ Pv ++ droplast(Match),St3};
 expr(#c_receive{anno=A,clauses=Ccs0,timeout=Ce,action=Ca}, Sub, St0) ->
     {Ke,Pe,St1} = atomic(Ce, Sub, St0),		%Force this to be atomic!
     {Rvar,St2} = new_var(St1),
@@ -847,15 +847,6 @@ foldr2(Fun, Acc0, [E1|L1], [E2|L2]) ->
     foldr2(Fun, Acc1, L1, L2);
 foldr2(_, Acc, [], []) -> Acc.
 
-%% first([A]) -> [A].
-%% last([A]) -> A.
-
-last([L]) -> L;
-last([_|T]) -> last(T).
-
-first([_]) -> [];
-first([H|T]) -> [H|first(T)].
-
 %% This code implements the algorithm for an optimizing compiler for
 %% pattern matching given "The Implementation of Functional
 %% Programming Languages" by Simon Peyton Jones. The code is much
diff --git a/lib/mnesia/test/mnesia_frag_test.erl b/lib/mnesia/test/mnesia_frag_test.erl
index d3f6762af7..6695fbc880 100644
--- a/lib/mnesia/test/mnesia_frag_test.erl
+++ b/lib/mnesia/test/mnesia_frag_test.erl
@@ -461,7 +461,7 @@ nice_iter_access(Tab, FragNames, RawRead) ->
     ExpectedLast = lists:last(Keys),
     ?match(ExpectedLast, mnesia:last(Tab)),
     
-    ExpectedAllPrev = ['$end_of_table' | lists:reverse(tl(lists:reverse(Keys)))],
+    ExpectedAllPrev = ['$end_of_table' | lists:droplast(Keys)],
     ?match(ExpectedAllPrev, lists:map(fun(K) -> mnesia:prev(Tab, K) end, Keys)),
     
     ExpectedAllNext = tl(Keys) ++ ['$end_of_table'],
@@ -477,7 +477,7 @@ evil_iter_access(Tab, FragNames, RawRead) ->
     ExpectedLast = lists:last(Keys),
     ?match(ExpectedLast, mnesia:last(Tab)),
     
-    ExpectedAllPrev = ['$end_of_table' | lists:reverse(tl(lists:reverse(Keys)))],
+    ExpectedAllPrev = ['$end_of_table' | lists:droplast(Keys)],
     ?match(ExpectedAllPrev, lists:map(fun(K) -> mnesia:prev(Tab, K) end, Keys)),
     
     ExpectedAllNext = tl(Keys) ++ ['$end_of_table'],
diff --git a/lib/orber/src/orber_interceptors.erl b/lib/orber/src/orber_interceptors.erl
index 407823ea79..62870b35b5 100644
--- a/lib/orber/src/orber_interceptors.erl
+++ b/lib/orber/src/orber_interceptors.erl
@@ -112,7 +112,7 @@ pop_system_message_interceptor(out) ->
 	[{_, []}] ->
 	    ok;
 	[{_, Interceptors}] ->
-	    ets:insert(orber_interceptors, {message_out_interceptors,  remove_last_element(Interceptors)});
+	    ets:insert(orber_interceptors, {message_out_interceptors,  lists:droplast(Interceptors)});
 	_ ->
 	    corba:raise(#'INTERNAL'{completion_status=?COMPLETED_NO})
     end.    
@@ -151,12 +151,3 @@ apply_message_interceptors([], F, ObjRef, Bytes) ->
 apply_message_interceptors([M | Rest], F, ObjRef, Bytes) ->
     apply_message_interceptors(Rest, F, ObjRef, apply(M, F, [ObjRef, Bytes])).
 
-
-remove_last_element([]) ->
-    [];
-remove_last_element([M]) ->
-    [];
-remove_last_element([M |Tail]) ->
-    remove_last_element([Tail]).
-
-    
diff --git a/lib/ssh/src/ssh_sftpd.erl b/lib/ssh/src/ssh_sftpd.erl
index 213b5c714d..52665635f0 100644
--- a/lib/ssh/src/ssh_sftpd.erl
+++ b/lib/ssh/src/ssh_sftpd.erl
@@ -673,7 +673,7 @@ resolve_symlinks_2(["." | RestPath], State0, LinkCnt, AccPath) ->
 resolve_symlinks_2([".." | RestPath], State0, LinkCnt, AccPath) ->
     %% Remove the last path component
     AccPathComps0 = filename:split(AccPath),
-    Path =  case lists:reverse(tl(lists:reverse(AccPathComps0))) of
+    Path =  case lists:droplast(AccPathComps0) of
 		[] ->
 		    "";
 		AccPathComps ->
diff --git a/lib/wx/api_gen/wx_gen.erl b/lib/wx/api_gen/wx_gen.erl
index 3ca8cd7d14..0f28b3dd5e 100644
--- a/lib/wx/api_gen/wx_gen.erl
+++ b/lib/wx/api_gen/wx_gen.erl
@@ -25,7 +25,7 @@
 
 -include_lib("xmerl/include/xmerl.hrl").
 
--import(lists, [foldl/3,foldr/3,reverse/1, keysearch/3, map/2, filter/2]).
+-import(lists, [foldl/3,foldr/3,reverse/1,keysearch/3,map/2,filter/2,droplast/1]).
 -import(proplists, [get_value/2,get_value/3]).
 
 -compile(export_all).
@@ -69,7 +69,7 @@ gen_code() ->
 gen_xml() ->
 %%     {ok, Defs} = file:consult("wxapi.conf"),
     
-%%     Rel = reverse(tl(reverse(os:cmd("wx-config --release")))),
+%%     Rel = droplast(os:cmd("wx-config --release")),
 %%     Dir = " /usr/include/wx-" ++ Rel ++ "/wx/",
 %%     Files0 = [Dir ++ File || {class, File, _, _, _} <- Defs],
 %%     Files1 = [Dir ++ File || {doxygen, File} <- Defs],
@@ -172,7 +172,7 @@ parse_defs([], Acc) -> reverse(Acc).
 meta_info(C=#class{name=CName,methods=Ms0}) ->
     Ms = lists:append(Ms0),
     HaveConstructor = lists:keymember(constructor, #method.method_type, Ms),
-    case lists:keysearch(destructor, #method.method_type, Ms) of
+    case keysearch(destructor, #method.method_type, Ms) of
 	false when HaveConstructor -> 
 	    Dest = #method{name = "destroy", id = next_id(func_id),
 			   method_type = destructor, params = [this(CName)]},
@@ -288,7 +288,7 @@ parse_attr1([{{attr,_}, #xmlElement{content=C, attributes=Attrs}}|R], AttrList0,
 parse_attr1([{_Id,_}|R],AttrList,Info, Res) ->
     parse_attr1(R,AttrList,Info, Res);
 parse_attr1([],Left,_, Res) ->
-    {lists:reverse(Res), Left}.
+    {reverse(Res), Left}.
 
 attr_acc(#param{name=N}, List) ->
     Name = list_to_atom(N),
@@ -994,7 +994,7 @@ erl_skip_opt2([F={_,{N,In,_},M=#method{where=Where}}|Ms],Acc1,Acc2,Check) ->
 		[] ->
 		    erl_skip_opt2(Ms,[F|Acc1],[M#method{where=erl_no_opt}|Acc2],[]);
 		_  ->
-		    Skipped = reverse(tl(reverse(In))),
+		    Skipped = droplast(In),
 		    T = fun({_,{_,Args,_},_}) -> true =:= types_differ(Skipped,Args) end,
 		    case lists:all(T, Check) of
 			true ->