Re: Only if the object exists

Hi,

At Sun, 12 Jun 2005 00:45:56 +0900,
Gavin Kistner wrote in [ruby-talk:145166]:
> Would it be possible to have the parser recognize the single-line 'if/ 
> unless' case and process the right side before the left side (the  
> order in which the code is executed)?

Not impossible, but a dirty hack because current implementation is one
pass parser.


Index: parse.y
===================================================================
RCS file: /cvs/ruby/src/ruby/parse.y,v
retrieving revision 1.387
diff -U2 -p -u -r1.387 parse.y
--- parse.y	12 Jun 2005 16:56:05 -0000	1.387
+++ parse.y	13 Jun 2005 09:11:49 -0000
@@ -150,4 +150,5 @@ struct parser_params {
     NODE *parser_eval_tree_begin;
     NODE *parser_eval_tree;
+    NODE *vcalls;
 #else
     /* Ripper only */
@@ -304,8 +305,16 @@ static void top_local_setup_gen _((struc
 #else
 #define remove_begin(node) (node)
+/* FIXME */
+# define local_cnt(x)      3
+# define local_id(x)       1
+# define dyna_in_block()   1
 #endif /* !RIPPER */
 static int lvar_defined_gen _((struct parser_params*, ID));
 #define lvar_defined(id) lvar_defined_gen(parser, id)
 
+#define lvar_count() (dyna_in_block() ? lvtbl->dname_size : lvtbl->cnt)
+static void replace_vcall _((struct parser_params *, int));
+static void merge_vcalls _((struct parser_params *));
+
 #define RE_OPTION_ONCE 0x80
 
@@ -678,4 +687,5 @@ stmts		: none
 		    /*%%%*/
 			$$ = block_append($1, newline_node(remove_begin($3)));
+			merge_vcalls(parser);
 		    /*%
 			$$ = dispatch2(stmts_add, $1, $3);
@@ -733,9 +743,14 @@ stmt		: kALIAS fitem {lex_state = EXPR_F
 		    %*/
 		    }
-		| stmt kIF_MOD expr_value
+		| stmt kIF_MOD
+		    {
+			$<num>$ = lvar_count();
+		    }
+		  expr_value
 		    {
 		    /*%%%*/
-			$$ = NEW_IF(cond($3), $1, 0);
-		        fixpos($$, $3);
+			replace_vcall(parser, $<num>3);
+			$$ = NEW_IF(cond($4), $1, 0);
+		        fixpos($$, $4);
 			if (cond_negative(&$$->nd_cond)) {
 		            $$->nd_else = $$->nd_body;
@@ -743,12 +758,17 @@ stmt		: kALIAS fitem {lex_state = EXPR_F
 			}
 		    /*%
-			$$ = dispatch2(if_mod, $3, $1);
+			$$ = dispatch2(if_mod, $4, $1);
 		    %*/
 		    }
-		| stmt kUNLESS_MOD expr_value
+		| stmt kUNLESS_MOD
+		    {
+			$<num>$ = lvar_count();
+		    }
+		  expr_value
 		    {
 		    /*%%%*/
-			$$ = NEW_UNLESS(cond($3), $1, 0);
-		        fixpos($$, $3);
+			replace_vcall(parser, $<num>3);
+			$$ = NEW_UNLESS(cond($4), $1, 0);
+		        fixpos($$, $4);
 			if (cond_negative(&$$->nd_cond)) {
 		            $$->nd_body = $$->nd_else;
@@ -756,15 +776,20 @@ stmt		: kALIAS fitem {lex_state = EXPR_F
 			}
 		    /*%
-		    	$$ = dispatch2(unless_mod, $3, $1);
+		    	$$ = dispatch2(unless_mod, $4, $1);
 		    %*/
 		    }
-		| stmt kWHILE_MOD expr_value
+		| stmt kWHILE_MOD
+		    {
+			$<num>$ = lvar_count();
+		    }
+		  expr_value
 		    {
 		    /*%%%*/
+			replace_vcall(parser, $<num>3);
 			if ($1 && nd_type($1) == NODE_BEGIN) {
-			    $$ = NEW_WHILE(cond($3), $1->nd_body, 0);
+			    $$ = NEW_WHILE(cond($4), $1->nd_body, 0);
 			}
 			else {
-			    $$ = NEW_WHILE(cond($3), $1, 1);
+			    $$ = NEW_WHILE(cond($4), $1, 1);
 			}
 			if (cond_negative(&$$->nd_cond)) {
@@ -772,15 +797,20 @@ stmt		: kALIAS fitem {lex_state = EXPR_F
 			}
 		    /*%
-			$$ = dispatch2(while_mod, $3, $1);
+			$$ = dispatch2(while_mod, $4, $1);
 		    %*/
 		    }
-		| stmt kUNTIL_MOD expr_value
+		| stmt kUNTIL_MOD
+		    {
+			$<num>$ = lvar_count();
+		    }
+		  expr_value
 		    {
 		    /*%%%*/
+			replace_vcall(parser, $<num>3);
 			if ($1 && nd_type($1) == NODE_BEGIN) {
-			    $$ = NEW_UNTIL(cond($3), $1->nd_body, 0);
+			    $$ = NEW_UNTIL(cond($4), $1->nd_body, 0);
 			}
 			else {
-			    $$ = NEW_UNTIL(cond($3), $1, 1);
+			    $$ = NEW_UNTIL(cond($4), $1, 1);
 			}
 			if (cond_negative(&$$->nd_cond)) {
@@ -788,5 +818,5 @@ stmt		: kALIAS fitem {lex_state = EXPR_F
 			}
 		    /*%
-			$$ = dispatch2(until_mod, $3, $1);
+			$$ = dispatch2(until_mod, $4, $1);
 		    %*/
 		    }
@@ -805,4 +835,5 @@ stmt		: kALIAS fitem {lex_state = EXPR_F
 			    yyerror("BEGIN in method");
 			}
+			$<node>1 = parser->vcalls;
 			local_push(0);
 		    /*%
@@ -818,4 +849,5 @@ stmt		: kALIAS fitem {lex_state = EXPR_F
 						            NEW_PREEXE($4));
 		        local_pop();
+			parser->vcalls = $<node>1;
 		        $$ = 0;
 		    /*%
@@ -2732,4 +2764,5 @@ primary		: literal
 			    yyerror("class definition in method body");
 			class_nest++;
+			$<node>1 = parser->vcalls;
 			local_push(0);
 		        $<num>$ = ruby_sourceline;
@@ -2747,4 +2780,5 @@ primary		: literal
 		        nd_set_line($$, $<num>4);
 		        local_pop();
+			parser->vcalls = $<node>1;
 			class_nest--;
 		    /*%
@@ -2768,4 +2802,5 @@ primary		: literal
 		        in_single = 0;
 			class_nest++;
+			$<node>1 = parser->vcalls;
 			local_push(0);
 		    /*%
@@ -2782,4 +2817,5 @@ primary		: literal
 		        fixpos($$, $3);
 		        local_pop();
+			parser->vcalls = $<node>1;
 			class_nest--;
 		        in_def = $<num>4;
@@ -2798,4 +2834,5 @@ primary		: literal
 			    yyerror("module definition in method body");
 			class_nest++;
+			$<node>1 = parser->vcalls;
 			local_push(0);
 		        $<num>$ = ruby_sourceline;
@@ -2813,4 +2850,5 @@ primary		: literal
 		        nd_set_line($$, $<num>3);
 		        local_pop();
+			parser->vcalls = $<node>1;
 			class_nest--;
 		    /*%
@@ -2825,4 +2863,5 @@ primary		: literal
 			cur_mid = $2;
 			in_def++;
+			$<node>1 = parser->vcalls;
 			local_push(0);
 		    /*%
@@ -2842,4 +2881,5 @@ primary		: literal
 		        fixpos($$, $4);
 		        local_pop();
+			parser->vcalls = $<node>1;
 			in_def--;
 			cur_mid = $<id>3;
@@ -2854,4 +2894,5 @@ primary		: literal
 		    /*%%%*/
 			in_single++;
+			$<node>1 = parser->vcalls;
 			local_push(0);
 		        lex_state = EXPR_END; /* force for args */
@@ -2871,4 +2912,5 @@ primary		: literal
 		        fixpos($$, $2);
 		        local_pop();
+			parser->vcalls = $<node>1;
 			in_single--;
 		    /*%
@@ -4317,11 +4359,4 @@ static int parser_here_document _((struc
 # define whole_match_p(e,l,i)      parser_whole_match_p(parser,e,l,i)
 
-#ifdef RIPPER
-/* FIXME */
-# define local_cnt(x)      3
-# define local_id(x)       1
-# define dyna_in_block()   1
-#endif /* RIPPER */
-
 #ifndef RIPPER
 # define set_yylval_str(x) yylval.node = NEW_STR(x)
@@ -7105,5 +7140,5 @@ gettable_gen(parser, id)
 	/* method call without arguments */
         dyna_check(id);
-	return NEW_VCALL(id);
+	return parser->vcalls = NEW_NODE(NODE_VCALL,0,id,parser->vcalls);
     }
     else if (is_global_id(id)) {
@@ -7915,4 +7950,6 @@ new_super(a)
 }
 
+#define NEW_VCALL_LIST(n) NEW_NODE(NODE_VCALL,0,0,n)
+
 static void
 local_push_gen(parser, top)
@@ -7932,4 +7969,5 @@ local_push_gen(parser, top)
     local->dyna_vars = ruby_dyna_vars;
     lvtbl = local;
+    parser->vcalls = NEW_VCALL_LIST(parser->vcalls);
     if (!top) {
 	/* preserve reference for GC, but link should be cut. */
@@ -7944,4 +7982,5 @@ local_pop_gen(parser)
 {
     struct local_vars *local = lvtbl->prev;
+    NODE *vcalls = parser->vcalls;
 
     if (lvtbl->tbl) {
@@ -7952,4 +7991,10 @@ local_pop_gen(parser)
 	xfree(lvtbl->dnames);
     }
+    while (vcalls) {
+	NODE *next = vcalls->nd_next;
+	vcalls->nd_next = 0;
+	vcalls = next;
+    }
+    parser->vcalls = 0;
     ruby_dyna_vars = lvtbl->dyna_vars;
     xfree(lvtbl);
@@ -8155,4 +8200,61 @@ dyna_init_gen(parser, node, pre)
 }
 
+static void
+merge_vcalls(parser)
+    struct parser_params *parser;
+{
+    NODE **prev, *n;
+
+    for (n = *(prev = &parser->vcalls); n != 0; n = n->nd_next) {
+	if (n->nd_mid == 0) {
+	    *prev = n->nd_next;
+	    n->nd_next = parser->vcalls;
+	    parser->vcalls = n;
+	    break;
+	}
+    }
+}
+
+static void
+replace_vcall(parser, vcnt)
+    struct parser_params *parser;
+    int vcnt;
+{
+    NODE **prev, *n;
+    ID id, *names;
+    int i, ncnt;
+    enum node_type type;
+
+    if (dyna_in_block()) {
+	if (!(names = lvtbl->dnames)) return;
+	ncnt = lvtbl->dname_size;
+	type = NODE_DVAR;
+    }
+    else {
+	if (!(names = lvtbl->tbl)) return;
+	names++;
+	ncnt = lvtbl->cnt;
+	if (vcnt < 2) vcnt = 2;
+	type = NODE_LVAR;
+    }
+
+    if (vcnt >= ncnt) return;
+    prev = &parser->vcalls;
+    while ((n = *prev) != 0 && (id = n->nd_mid) != 0) {
+	for (i = vcnt; i < ncnt; ++i) {
+	    if (id == names[i]) {
+		*prev = n->nd_next;
+		nd_set_type(n, type);
+		n->nd_mid = 0;
+		n->nd_vid = id;
+		n->nd_cnt = (type == NODE_LVAR) ? i : 0;
+		goto skip;
+	    }
+	}
+	prev = &n->nd_next;
+      skip:;
+    }
+}
+
 void
 rb_gc_mark_parser()
@@ -8554,4 +8656,5 @@ parser_initialize(parser)
     parser->parser_eval_tree_begin = 0;
     parser->parser_eval_tree = 0;
+    parser->vcalls = 0;
 #else
     parser->parser_ruby_sourcefile = Qnil;


-- 
Nobu Nakada