Patch 8.2.2321

[Bram Moolenaar]

Patch 8.2.2321
Problem: Vim9: cannot nest closures.
Solution: Add the nesting level to ISN_LOADOUTER and ISN_STOREOUTER.
(closes #7150, closes #7635)
Files: src/vim9.h, src/vim9compile.c, src/vim9execute.c, src/structs.h,
src/testdir/test_vim9_disassemble.vim,
src/testdir/test_vim9_func.vim


*** ../vim-8.2.2320/src/vim9.h 2021-01-09 15:45:20.353451132 +0100
--- src/vim9.h 2021-01-09 18:42:27.619303000 +0100
***************
*** 33,39 ****
ISN_LOADWDICT, // push w: dict
ISN_LOADTDICT, // push t: dict
ISN_LOADS, // push s: variable isn_arg.loadstore
! ISN_LOADOUTER, // push variable from outer scope isn_arg.number
ISN_LOADSCRIPT, // push script-local variable isn_arg.script.
ISN_LOADOPT, // push option isn_arg.string
ISN_LOADENV, // push environment variable isn_arg.string
--- 33,39 ----
ISN_LOADWDICT, // push w: dict
ISN_LOADTDICT, // push t: dict
ISN_LOADS, // push s: variable isn_arg.loadstore
! ISN_LOADOUTER, // push variable from outer scope isn_arg.outer
ISN_LOADSCRIPT, // push script-local variable isn_arg.script.
ISN_LOADOPT, // push option isn_arg.string
ISN_LOADENV, // push environment variable isn_arg.string
***************
*** 47,53 ****
ISN_STOREW, // pop into window-local variable isn_arg.string
ISN_STORET, // pop into tab-local variable isn_arg.string
ISN_STORES, // pop into script variable isn_arg.loadstore
! ISN_STOREOUTER, // pop variable into outer scope isn_arg.number
ISN_STORESCRIPT, // pop into script variable isn_arg.script
ISN_STOREOPT, // pop into option isn_arg.string
ISN_STOREENV, // pop into environment variable isn_arg.string
--- 47,53 ----
ISN_STOREW, // pop into window-local variable isn_arg.string
ISN_STORET, // pop into tab-local variable isn_arg.string
ISN_STORES, // pop into script variable isn_arg.loadstore
! ISN_STOREOUTER, // pop variable into outer scope isn_arg.outer
ISN_STORESCRIPT, // pop into script variable isn_arg.script
ISN_STOREOPT, // pop into option isn_arg.string
ISN_STOREENV, // pop into environment variable isn_arg.string
***************
*** 303,308 ****
--- 303,314 ----
int unp_semicolon; // last item gets list of remainder
} unpack_T;

+ // arguments to ISN_LOADOUTER and ISN_STOREOUTER
+ typedef struct {
+ int outer_idx; // index
+ int outer_depth; // nesting level, stack frames to go up
+ } outer_T;
+
/*
* Instruction
*/
***************
*** 342,347 ****
--- 348,354 ----
put_T put;
cmod_T cmdmod;
unpack_T unpack;
+ outer_T outer;
} isn_arg;
};

*** ../vim-8.2.2320/src/vim9compile.c 2021-01-09 15:45:20.353451132 +0100
--- src/vim9compile.c 2021-01-10 13:58:31.034647994 +0100
***************
*** 108,114 ****
char_u *lv_name;
type_T *lv_type;
int lv_idx; // index of the variable on the stack
! int lv_from_outer; // when TRUE using ctx_outer scope
int lv_const; // when TRUE cannot be assigned to
int lv_arg; // when TRUE this is an argument
} lvar_T;
--- 108,114 ----
char_u *lv_name;
type_T *lv_type;
int lv_idx; // index of the variable on the stack
! int lv_from_outer; // nesting level, using ctx_outer scope
int lv_const; // when TRUE cannot be assigned to
int lv_arg; // when TRUE this is an argument
} lvar_T;
***************
*** 149,155 ****

/*
* Lookup variable "name" in the local scope and return it in "lvar".
! * "lvar->lv_from_outer" is set accordingly.
* If "lvar" is NULL only check if the variable can be found.
* Return FAIL if not found.
*/
--- 149,155 ----

/*
* Lookup variable "name" in the local scope and return it in "lvar".
! * "lvar->lv_from_outer" is incremented accordingly.
* If "lvar" is NULL only check if the variable can be found.
* Return FAIL if not found.
*/
***************
*** 172,178 ****
if (lvar != NULL)
{
*lvar = *lvp;
! lvar->lv_from_outer = FALSE;
}
return OK;
}
--- 172,178 ----
if (lvar != NULL)
{
*lvar = *lvp;
! lvar->lv_from_outer = 0;
}
return OK;
}
***************
*** 186,192 ****
if (lvar != NULL)
{
cctx->ctx_outer_used = TRUE;
! lvar->lv_from_outer = TRUE;
}
return OK;
}
--- 186,192 ----
if (lvar != NULL)
{
cctx->ctx_outer_used = TRUE;
! ++lvar->lv_from_outer;
}
return OK;
}
***************
*** 258,264 ****
if (arg_exists(name, len, idxp, type, gen_load_outer, cctx->ctx_outer)
== OK)
{
! *gen_load_outer = TRUE;
return OK;
}
}
--- 258,264 ----
if (arg_exists(name, len, idxp, type, gen_load_outer, cctx->ctx_outer)
== OK)
{
! ++*gen_load_outer;
return OK;
}
}
***************
*** 1176,1181 ****
--- 1176,1198 ----
}

/*
+ * Generate an ISN_STOREOUTER instruction.
+ */
+ static int
+ generate_STOREOUTER(cctx_T *cctx, int idx, int level)
+ {
+ isn_T *isn;
+
+ RETURN_OK_IF_SKIP(cctx);
+ if ((isn = generate_instr_drop(cctx, ISN_STOREOUTER, 1)) == NULL)
+ return FAIL;
+ isn->isn_arg.outer.outer_idx = idx;
+ isn->isn_arg.outer.outer_depth = level;
+
+ return OK;
+ }
+
+ /*
* Generate an ISN_STORENR instruction (short for ISN_PUSHNR + ISN_STORE)
*/
static int
***************
*** 1234,1239 ****
--- 1251,1277 ----
}

/*
+ * Generate an ISN_LOADOUTER instruction
+ */
+ static int
+ generate_LOADOUTER(
+ cctx_T *cctx,
+ int idx,
+ int nesting,
+ type_T *type)
+ {
+ isn_T *isn;
+
+ RETURN_OK_IF_SKIP(cctx);
+ if ((isn = generate_instr_type(cctx, ISN_LOADOUTER, type)) == NULL)
+ return FAIL;
+ isn->isn_arg.outer.outer_idx = idx;
+ isn->isn_arg.outer.outer_depth = nesting;
+
+ return OK;
+ }
+
+ /*
* Generate an ISN_LOADV instruction for v:var.
*/
static int
***************
*** 1439,1444 ****
--- 1477,1487 ----
isn->isn_arg.funcref.fr_func = ufunc->uf_dfunc_idx;
cctx->ctx_has_closure = 1;

+ // if the referenced function is a closure, it may use items further up in
+ // the nested context, including this one.
+ if (ufunc->uf_flags & FC_CLOSURE)
+ cctx->ctx_ufunc->uf_flags |= FC_CLOSURE;
+
if (ga_grow(stack, 1) == FAIL)
return FAIL;
((type_T **)stack->ga_data)[stack->ga_len] =
***************
*** 2589,2595 ****
size_t len = end - *arg;
int idx;
int gen_load = FALSE;
! int gen_load_outer = FALSE;

name = vim_strnsave(*arg, end - *arg);
if (name == NULL)
--- 2632,2638 ----
size_t len = end - *arg;
int idx;
int gen_load = FALSE;
! int gen_load_outer = 0;

name = vim_strnsave(*arg, end - *arg);
if (name == NULL)
***************
*** 2597,2603 ****

if (arg_exists(*arg, len, &idx, &type, &gen_load_outer, cctx) == OK)
{
! if (!gen_load_outer)
gen_load = TRUE;
}
else
--- 2640,2646 ----

if (arg_exists(*arg, len, &idx, &type, &gen_load_outer, cctx) == OK)
{
! if (gen_load_outer == 0)
gen_load = TRUE;
}
else
***************
*** 2608,2615 ****
{
type = lvar.lv_type;
idx = lvar.lv_idx;
! if (lvar.lv_from_outer)
! gen_load_outer = TRUE;
else
gen_load = TRUE;
}
--- 2651,2658 ----
{
type = lvar.lv_type;
idx = lvar.lv_idx;
! if (lvar.lv_from_outer != 0)
! gen_load_outer = lvar.lv_from_outer;
else
gen_load = TRUE;
}
***************
*** 2631,2639 ****
}
if (gen_load)
res = generate_LOAD(cctx, ISN_LOAD, idx, NULL, type);
! if (gen_load_outer)
{
! res = generate_LOAD(cctx, ISN_LOADOUTER, idx, NULL, type);
cctx->ctx_outer_used = TRUE;
}
}
--- 2674,2682 ----
}
if (gen_load)
res = generate_LOAD(cctx, ISN_LOAD, idx, NULL, type);
! if (gen_load_outer > 0)
{
! res = generate_LOADOUTER(cctx, idx, gen_load_outer, type);
cctx->ctx_outer_used = TRUE;
}
}
***************
*** 5120,5128 ****
generate_LOADV(cctx, name + 2, TRUE);
break;
case dest_local:
! if (lvar->lv_from_outer)
! generate_LOAD(cctx, ISN_LOADOUTER, lvar->lv_idx,
! NULL, type);
else
generate_LOAD(cctx, ISN_LOAD, lvar->lv_idx, NULL, type);
break;
--- 5163,5171 ----
generate_LOADV(cctx, name + 2, TRUE);
break;
case dest_local:
! if (lvar->lv_from_outer > 0)
! generate_LOADOUTER(cctx, lvar->lv_idx, lvar->lv_from_outer,
! type);
else
generate_LOAD(cctx, ISN_LOAD, lvar->lv_idx, NULL, type);
break;
***************
*** 6178,6184 ****

// optimization: turn "var = 123" from ISN_PUSHNR +
// ISN_STORE into ISN_STORENR
! if (!lhs.lhs_lvar->lv_from_outer
&& instr->ga_len == instr_count + 1
&& isn->isn_type == ISN_PUSHNR)
{
--- 6221,6227 ----

// optimization: turn "var = 123" from ISN_PUSHNR +
// ISN_STORE into ISN_STORENR
! if (lhs.lhs_lvar->lv_from_outer == 0
&& instr->ga_len == instr_count + 1
&& isn->isn_type == ISN_PUSHNR)
{
***************
*** 6190,6198 ****
if (stack->ga_len > 0)
--stack->ga_len;
}
! else if (lhs.lhs_lvar->lv_from_outer)
! generate_STORE(cctx, ISN_STOREOUTER,
! lhs.lhs_lvar->lv_idx, NULL);
else
generate_STORE(cctx, ISN_STORE, lhs.lhs_lvar->lv_idx, NULL);
}
--- 6233,6241 ----
if (stack->ga_len > 0)
--stack->ga_len;
}
! else if (lhs.lhs_lvar->lv_from_outer > 0)
! generate_STOREOUTER(cctx, lhs.lhs_lvar->lv_idx,
! lhs.lhs_lvar->lv_from_outer);
else
generate_STORE(cctx, ISN_STORE, lhs.lhs_lvar->lv_idx, NULL);
}
*** ../vim-8.2.2320/src/vim9execute.c 2021-01-09 15:45:20.353451132 +0100
--- src/vim9execute.c 2021-01-10 13:36:30.598677638 +0100
***************
*** 60,65 ****
--- 60,67 ----

garray_T *ec_outer_stack; // stack used for closures
int ec_outer_frame; // stack frame in ec_outer_stack
+ garray_T *ec_outer_up_stack; // ec_outer_stack one level up
+ int ec_outer_up_frame; // ec_outer_frame one level up

garray_T ec_trystack; // stack of trycmd_T values
int ec_in_catch; // when TRUE in catch or finally block
***************
*** 149,154 ****
--- 151,158 ----

/*
* Call compiled function "cdf_idx" from compiled code.
+ * This adds a stack frame and sets the instruction pointer to the start of the
+ * called function.
*
* Stack has:
* - current arguments (already there)
***************
*** 248,253 ****
--- 252,258 ----
STACK_TV_BOT(2)->vval.v_string = (void *)ectx->ec_outer_stack;
STACK_TV_BOT(3)->vval.v_number = ectx->ec_outer_frame;
STACK_TV_BOT(4)->vval.v_number = ectx->ec_frame_idx;
+ // TODO: save ec_outer_up_stack as well?
ectx->ec_frame_idx = ectx->ec_stack.ga_len;

// Initialize local variables
***************
*** 266,271 ****
--- 271,285 ----
{
ectx->ec_outer_stack = ufunc->uf_partial->pt_ectx_stack;
ectx->ec_outer_frame = ufunc->uf_partial->pt_ectx_frame;
+ ectx->ec_outer_up_stack = ufunc->uf_partial->pt_outer_stack;
+ ectx->ec_outer_up_frame = ufunc->uf_partial->pt_outer_frame;
+ }
+ else if (ufunc->uf_flags & FC_CLOSURE)
+ {
+ ectx->ec_outer_stack = &ectx->ec_stack;
+ ectx->ec_outer_frame = ectx->ec_frame_idx;
+ ectx->ec_outer_up_stack = ectx->ec_outer_stack;
+ ectx->ec_outer_up_frame = ectx->ec_outer_frame;
}

// Set execution state to the start of the called function.
***************
*** 417,422 ****
--- 431,438 ----
pt->pt_funcstack = funcstack;
pt->pt_ectx_stack = &funcstack->fs_ga;
pt->pt_ectx_frame = ectx->ec_frame_idx - top;
+ pt->pt_outer_stack = ectx->ec_outer_stack;
+ pt->pt_outer_frame = ectx->ec_outer_frame;
}
}
}
***************
*** 598,603 ****
--- 614,622 ----

/*
* Execute a user defined function.
+ * If the function is compiled this will add a stack frame and set the
+ * instruction pointer at the start of the function.
+ * Otherwise the function is called here.
* "iptr" can be used to replace the instruction with a more efficient one.
*/
static int
***************
*** 743,753 ****

if (pt->pt_func != NULL)
{
int ret = call_ufunc(pt->pt_func, argcount, ectx, NULL);

! // closure may need the function context where it was defined
! ectx->ec_outer_stack = pt->pt_ectx_stack;
! ectx->ec_outer_frame = pt->pt_ectx_frame;

return ret;
}
--- 762,779 ----

if (pt->pt_func != NULL)
{
+ int frame_idx = ectx->ec_frame_idx;
int ret = call_ufunc(pt->pt_func, argcount, ectx, NULL);

! if (ectx->ec_frame_idx != frame_idx)
! {
! // call_dfunc() added a stack frame, closure may need the
! // function context where it was defined.
! ectx->ec_outer_stack = pt->pt_ectx_stack;
! ectx->ec_outer_frame = pt->pt_ectx_frame;
! ectx->ec_outer_up_stack = pt->pt_outer_stack;
! ectx->ec_outer_up_frame = pt->pt_outer_frame;
! }

return ret;
}
***************
*** 1041,1046 ****
--- 1067,1074 ----
// variables in the current stack.
pt->pt_ectx_stack = &ectx->ec_stack;
pt->pt_ectx_frame = ectx->ec_frame_idx;
+ pt->pt_outer_stack = ectx->ec_outer_stack;
+ pt->pt_outer_frame = ectx->ec_outer_frame;

// If this function returns and the closure is still
// being used, we need to make a copy of the context
***************
*** 1220,1236 ****
--- 1248,1270 ----
// TODO: is this always the right way?
ectx.ec_outer_stack = &current_ectx->ec_stack;
ectx.ec_outer_frame = current_ectx->ec_frame_idx;
+ ectx.ec_outer_up_stack = current_ectx->ec_outer_stack;
+ ectx.ec_outer_up_frame = current_ectx->ec_outer_frame;
}
else
{
ectx.ec_outer_stack = partial->pt_ectx_stack;
ectx.ec_outer_frame = partial->pt_ectx_frame;
+ ectx.ec_outer_up_stack = partial->pt_outer_stack;
+ ectx.ec_outer_up_frame = partial->pt_outer_frame;
}
}
else if (ufunc->uf_partial != NULL)
{
ectx.ec_outer_stack = ufunc->uf_partial->pt_ectx_stack;
ectx.ec_outer_frame = ufunc->uf_partial->pt_ectx_frame;
+ ectx.ec_outer_up_stack = ufunc->uf_partial->pt_outer_stack;
+ ectx.ec_outer_up_frame = ufunc->uf_partial->pt_outer_frame;
}

// dummy frame entries
***************
*** 1514,1524 ****

// load variable or argument from outer scope
case ISN_LOADOUTER:
! if (GA_GROW(&ectx.ec_stack, 1) == FAIL)
! goto failed;
! copy_tv(STACK_OUT_TV_VAR(iptr->isn_arg.number),
STACK_TV_BOT(0));
! ++ectx.ec_stack.ga_len;
break;

// load v: variable
--- 1548,1577 ----

// load variable or argument from outer scope
case ISN_LOADOUTER:
! {
! typval_T *stack;
! int depth = iptr->isn_arg.outer.outer_depth;
!
! if (GA_GROW(&ectx.ec_stack, 1) == FAIL)
! goto failed;
! if (depth <= 1)
! stack = ((typval_T *)ectx.ec_outer_stack->ga_data)
! + ectx.ec_outer_frame;
! else if (depth == 2)
! stack = ((typval_T *)ectx.ec_outer_up_stack->ga_data)
! + ectx.ec_outer_up_frame;
! else
! {
! SOURCING_LNUM = iptr->isn_lnum;
! iemsg("LOADOUTER level > 2 not supported yet");
! goto failed;
! }
!
! copy_tv(stack + STACK_FRAME_SIZE
! + iptr->isn_arg.outer.outer_idx,
STACK_TV_BOT(0));
! ++ectx.ec_stack.ga_len;
! }
break;

// load v: variable
***************
*** 1719,1725 ****
// store variable or argument in outer scope
case ISN_STOREOUTER:
--ectx.ec_stack.ga_len;
! tv = STACK_OUT_TV_VAR(iptr->isn_arg.number);
clear_tv(tv);
*tv = *STACK_TV_BOT(0);
break;
--- 1772,1779 ----
// store variable or argument in outer scope
case ISN_STOREOUTER:
--ectx.ec_stack.ga_len;
! // TODO: use outer_depth
! tv = STACK_OUT_TV_VAR(iptr->isn_arg.outer.outer_idx);
clear_tv(tv);
*tv = *STACK_TV_BOT(0);
break;
***************
*** 3622,3638 ****
(varnumber_T)(iptr->isn_arg.number));
break;
case ISN_LOAD:
- case ISN_LOADOUTER:
{
- char *add = iptr->isn_type == ISN_LOAD ? "" : "OUTER";
-
if (iptr->isn_arg.number < 0)
! smsg("%4d LOAD%s arg[%lld]", current, add,
(varnumber_T)(iptr->isn_arg.number
+ STACK_FRAME_SIZE));
else
! smsg("%4d LOAD%s $%lld", current, add,
! (varnumber_T)(iptr->isn_arg.number));
}
break;
case ISN_LOADV:
--- 3676,3702 ----
(varnumber_T)(iptr->isn_arg.number));
break;
case ISN_LOAD:
{
if (iptr->isn_arg.number < 0)
! smsg("%4d LOAD arg[%lld]", current,
(varnumber_T)(iptr->isn_arg.number
+ STACK_FRAME_SIZE));
else
! smsg("%4d LOAD $%lld", current,
! (varnumber_T)(iptr->isn_arg.number));
! }
! break;
! case ISN_LOADOUTER:
! {
! if (iptr->isn_arg.number < 0)
! smsg("%4d LOADOUTER level %d arg[%d]", current,
! iptr->isn_arg.outer.outer_depth,
! iptr->isn_arg.outer.outer_idx
! + STACK_FRAME_SIZE);
! else
! smsg("%4d LOADOUTER level %d $%d", current,
! iptr->isn_arg.outer.outer_depth,
! iptr->isn_arg.outer.outer_idx);
}
break;
case ISN_LOADV:
***************
*** 3699,3714 ****
break;

case ISN_STORE:
case ISN_STOREOUTER:
{
- char *add = iptr->isn_type == ISN_STORE ? "" : "OUTER";
-
if (iptr->isn_arg.number < 0)
! smsg("%4d STORE%s arg[%lld]", current, add,
! (varnumber_T)(iptr->isn_arg.number + STACK_FRAME_SIZE));
else
! smsg("%4d STORE%s $%lld", current, add,
! (varnumber_T)(iptr->isn_arg.number));
}
break;
case ISN_STOREV:
--- 3763,3784 ----
break;

case ISN_STORE:
+ if (iptr->isn_arg.number < 0)
+ smsg("%4d STORE arg[%lld]", current,
+ iptr->isn_arg.number + STACK_FRAME_SIZE);
+ else
+ smsg("%4d STORE $%lld", current, iptr->isn_arg.number);
+ break;
case ISN_STOREOUTER:
{
if (iptr->isn_arg.number < 0)
! smsg("%4d STOREOUTEr level %d arg[%d]", current,
! iptr->isn_arg.outer.outer_depth,
! iptr->isn_arg.outer.outer_idx + STACK_FRAME_SIZE);
else
! smsg("%4d STOREOUTER level %d $%d", current,
! iptr->isn_arg.outer.outer_depth,
! iptr->isn_arg.outer.outer_idx);
}
break;
case ISN_STOREV:
*** ../vim-8.2.2320/src/structs.h 2021-01-09 15:45:20.353451132 +0100
--- src/structs.h 2021-01-10 12:15:48.701453238 +0100
***************
*** 1978,1983 ****
--- 1978,1985 ----
// For a compiled closure: the arguments and local variables.
garray_T *pt_ectx_stack; // where to find local vars
int pt_ectx_frame; // index of function frame in uf_ectx_stack
+ garray_T *pt_outer_stack; // pt_ectx_stack one level up
+ int pt_outer_frame; // pt_ectx_frame one level up.
funcstack_T *pt_funcstack; // copy of stack, used after context
// function returns

*** ../vim-8.2.2320/src/testdir/test_vim9_disassemble.vim 2021-01-08 20:53:05.736404852 +0100
--- src/testdir/test_vim9_disassemble.vim 2021-01-09 19:13:45.530512401 +0100
***************
*** 567,583 ****
var res = execute('disass g:Append')
assert_match('<lambda>\d\_s*' ..
'local ..= arg\_s*' ..
! '\d LOADOUTER $0\_s*' ..
'\d LOAD arg\[-1\]\_s*' ..
'\d CONCAT\_s*' ..
! '\d STOREOUTER $0\_s*' ..
'\d RETURN 0',
res)

res = execute('disass g:Get')
assert_match('<lambda>\d\_s*' ..
'return local\_s*' ..
! '\d LOADOUTER $0\_s*' ..
'\d RETURN',
res)

--- 567,583 ----
var res = execute('disass g:Append')
assert_match('<lambda>\d\_s*' ..
'local ..= arg\_s*' ..
! '\d LOADOUTER level 1 $0\_s*' ..
'\d LOAD arg\[-1\]\_s*' ..
'\d CONCAT\_s*' ..
! '\d STOREOUTER level 1 $0\_s*' ..
'\d RETURN 0',
res)

res = execute('disass g:Get')
assert_match('<lambda>\d\_s*' ..
'return local\_s*' ..
! '\d LOADOUTER level 1 $0\_s*' ..
'\d RETURN',
res)

*** ../vim-8.2.2320/src/testdir/test_vim9_func.vim 2021-01-08 22:24:16.467725889 +0100
--- src/testdir/test_vim9_func.vim 2021-01-10 13:52:43.599603841 +0100
***************
*** 1812,1817 ****
--- 1812,1827 ----
assert_match('def <lambda>\d\+(_: any, ...): number\n1 return 0\n enddef', body)
enddef

+ def DoFilterThis(a: string): list<string>
+ # closure nested inside another closure using argument
+ var Filter = (l) => filter(l, (_, v) => stridx(v, a) == 0)
+ return ['x', 'y', 'a', 'x2', 'c']->Filter()
+ enddef
+
+ def Test_nested_closure_using_argument()
+ assert_equal(['x', 'x2'], DoFilterThis('x'))
+ enddef
+
func Test_silent_echo()
CheckScreendump

*** ../vim-8.2.2320/src/version.c 2021-01-09 16:21:34.000353394 +0100
--- src/version.c 2021-01-09 18:43:59.655077205 +0100
***************
*** 752,753 ****
--- 752,755 ----
{ /* Add new patch number below this line */
+ /**/
+ 2321,
/**/

--
hundred-and-one symptoms of being an internet addict:
119. You are reading a book and look for the scroll bar to get to
the next page.

/// Bram Moolenaar -- Br...@Moolenaar.net -- http://www.Moolenaar.net \\\
/// sponsor Vim, vote for features -- http://www.Vim.org/sponsor/ \\\
\\\ an exciting new programming language -- http://www.Zimbu.org ///
\\\ help me help AIDS victims -- http://ICCF-Holland.org ///