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Scattering `for' notation #10

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4 changes: 4 additions & 0 deletions ChangeLog.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -2295,3 +2295,7 @@ Version 1.8.0p5, 12 May 1996
36789.foo
(an understandable typo for #6789.foo) stopped compiling when found in a
database made by a pre-1.8.0 server.

Version X, in progress
**** Changes relevant to programmers / wizards:
-- Added support for scattering in `for' statements.
96 changes: 87 additions & 9 deletions parser.y
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Original file line number Diff line number Diff line change
Expand Up @@ -51,19 +51,21 @@ static DB_Version language_version;
static void error(const char *, const char *);
static void warning(const char *, const char *);
static int find_id(char *name);
static const char *get_name_from_id(int);
static void yyerror(const char *s);
static int yylex(void);
static Scatter *scatter_from_arglist(Arg_List *);
static Scatter *add_scatter_item(Scatter *, Scatter *);
static void vet_scatter(Scatter *);
static void push_loop_name(const char *);
static void push_loop_name_with_id(const char *, int);
static void pop_loop_name(void);
static void suspend_loop_scope(void);
static void resume_loop_scope(void);

enum loop_exit_kind { LOOP_BREAK, LOOP_CONTINUE };

static void check_loop_name(const char *, enum loop_exit_kind);
static int check_loop_name(char *, enum loop_exit_kind);
%}

%union {
Expand All @@ -86,7 +88,7 @@ static void check_loop_name(const char *, enum loop_exit_kind);
%type <args> arglist ne_arglist codes
%type <except> except excepts
%type <string> opt_id
%type <scatter> scatter scatter_item
%type <scatter> scatter_any scatter scatter_item

%token <integer> tINTEGER
%token <object> tOBJECT
Expand Down Expand Up @@ -140,6 +142,47 @@ statement:
$$->s.cond.arms->next = $6;
$$->s.cond.otherwise = $7;
}
| tFOR '{' scatter_any '}' tIN '(' expr ')'
{
const char *vname;
Stream *s;
int id;

if (!$3) {
yyerror("Empty list in scattering for.");
return 0;
}

vet_scatter($3);
vname = get_name_from_id($3->id);
s = new_stream(8);
stream_printf(s, "@%s", vname);
id = find_id(alloc_string(stream_contents(s)));
free_stream(s);
push_loop_name_with_id(vname, id);

$<integer>$ = id;
}
statements tENDFOR
{
Stmt *s;
Expr *lhs, *rhs;
int id = $<integer>9;

lhs = alloc_expr(EXPR_SCATTER);
lhs->e.scatter = $3;
rhs = alloc_expr(EXPR_ID);
rhs->e.id = id;
s = alloc_stmt(STMT_EXPR);
s->s.expr = alloc_binary(EXPR_ASGN, lhs, rhs);
s->next = $10;

$$ = alloc_stmt(STMT_LIST);
$$->s.list.id = id;
$$->s.list.expr = $7;
$$->s.list.body = s;
pop_loop_name();
}
| tFOR tID tIN '(' expr ')'
{
push_loop_name($2);
Expand Down Expand Up @@ -226,9 +269,10 @@ statement:
}
| tBREAK tID ';'
{
int id =
check_loop_name($2, LOOP_BREAK);
$$ = alloc_stmt(STMT_BREAK);
$$->s.exit = find_id($2);
$$->s.exit = id;
}
| tCONTINUE ';'
{
Expand All @@ -238,9 +282,10 @@ statement:
}
| tCONTINUE tID ';'
{
int id =
check_loop_name($2, LOOP_CONTINUE);
$$ = alloc_stmt(STMT_CONTINUE);
$$->s.exit = find_id($2);
$$->s.exit = id;
}
| tRETURN expr ';'
{
Expand Down Expand Up @@ -640,6 +685,17 @@ ne_arglist:
}
;

scatter_any:
arglist
{
$$ = scatter_from_arglist($1);
}
| scatter
{
$$ = $1;
}
;

scatter:
ne_arglist ',' scatter_item
{
Expand Down Expand Up @@ -695,6 +751,12 @@ find_id(char *name)
return slot;
}

static const char*
get_name_from_id(int id)
{
return local_names->names[id];
}

static void
yyerror(const char *s)
{
Expand Down Expand Up @@ -1008,21 +1070,29 @@ struct loop_entry {
struct loop_entry *next;
const char *name;
int is_barrier;
int id;
};

static struct loop_entry *loop_stack;

static void
push_loop_name(const char *name)
push_loop_name_with_id(const char *name, int id)
{
struct loop_entry *entry = mymalloc(sizeof(struct loop_entry), M_AST);

entry->next = loop_stack;
entry->name = (name ? str_dup(name) : 0);
entry->is_barrier = 0;
entry->id = id;
loop_stack = entry;
}

static void
push_loop_name(const char *name)
{
push_loop_name_with_id(name, -1);
}

static void
pop_loop_name(void)
{
Expand Down Expand Up @@ -1066,8 +1136,8 @@ resume_loop_scope(void)
}
}

static void
check_loop_name(const char *name, enum loop_exit_kind kind)
static int
check_loop_name(char *name, enum loop_exit_kind kind)
{
struct loop_entry *entry;

Expand All @@ -1078,17 +1148,25 @@ check_loop_name(const char *name, enum loop_exit_kind kind)
else
yyerror("No enclosing loop for `continue' statement");
}
return;
return -1;
}

for (entry = loop_stack; entry && !entry->is_barrier; entry = entry->next)
if (entry->name && mystrcasecmp(entry->name, name) == 0)
return;
{
if (entry->id == -1)
entry->id = find_id(name);
else
dealloc_string(name);
return entry->id;
}

if (kind == LOOP_BREAK)
error("Invalid loop name in `break' statement: ", name);
else
error("Invalid loop name in `continue' statement: ", name);
dealloc_string(name);
return -1;
}

Program *
Expand Down
32 changes: 30 additions & 2 deletions unparse.c
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Expand Up @@ -271,12 +271,40 @@ unparse_stmt_cond(Stream *str, struct Stmt_Cond cond, int indent)
static void
unparse_stmt_list(Stream *str, struct Stmt_List list, int indent)
{
stream_printf(str, "for %s in (", prog->var_names[list.id]);
const char *vname = prog->var_names[list.id];
Stmt *body = list.body;

stream_add_string(str, "for ");
if (vname[0] == '@' &&
body->kind == STMT_EXPR &&
body->s.expr->kind == EXPR_ASGN &&
body->s.expr->e.bin.rhs->kind == EXPR_ID &&
body->s.expr->e.bin.rhs->e.id == list.id &&
body->s.expr->e.bin.lhs->kind == EXPR_SCATTER) {
unparse_expr(str, body->s.expr->e.bin.lhs);
/* NOTE: if programmers are ever allowed to put '@' in their own
* break/continue statements, this could protentially lead to a
* decompile-then-recompile inconsistency. For example:
* for {a, b} in (c)
* for a in (a) would continue the *outer* loop
* continue @a; <-- initially, but decompile as "continue
* endfor a" and then recompile to continue the
* endfor inner loop instead
* This could also happen without extending the syntax, by
* allowing programmers to modify the bytecode other ways (eg,
* an assembler/debugger).
*/
prog->var_names[list.id] = &prog->var_names[list.id][1];
body = body->next;
} else
stream_add_string(str, vname);
stream_add_string(str, " in (");
unparse_expr(str, list.expr);
stream_add_char(str, ')');
output(str);
unparse_stmt(list.body, indent + 2);
unparse_stmt(body, indent + 2);
indent_stmt(str, indent);
prog->var_names[list.id] = vname;
stream_add_string(str, "endfor");
output(str);
}
Expand Down