bug(?) when using symbols for variables/methods

[Mark Hubbart]

Hi, all

Is this a bug, a feature, or just something weird?

irb(main):001:0> class Foo; def initialize(bar); @23 = bar; end; end
SyntaxError: compile error
(irb):1: `@2' is not allowed as an instance variable name
from (irb):1
irb(main):002:0> class Foo; end
=> nil
irb(main):003:0> f=Foo.new
=> #<Foo:0x46aa8>
irb(main):004:0> f.instance_variable_set@23, 23)
SyntaxError: compile error
(irb):4: `@2' is not allowed as an instance variable name
from (irb):4
irb(main):005:0> f.instance_variable_set"@23", 23)
=> 23
irb(main):006:0> f
=> #<Foo:0x46aa8 @23=23>
irb(main):007:0> RUBY_VERSION
=> "1.9.0"

@23 is an illegal instance variable. (yup)

- In line 1, I tried setting it in #initialize. didn't work, as
expected.
- line 4, tried setting using a normal symbol. again, didn't work.
- line 5, tried setting it using a quoted symbol. Somehow, it works...

I realize that this is contrived. But it *is* a little odd, isn't it?
If you do the same trick with attr_reader/attr_writer, you can create
accessor functions for the variable. "23" and "23=" show up in the
methods() array. You can call them, but only using foo.send"23=",
42).

--Mark

 

[nobu.nokada]

Hi,

At Wed, 3 Mar 2004 05:20:48 +0900,
Mark Hubbart wrote in [ruby-talk:94087]:

I realize that this is contrived. But it *is* a little odd, isn't it?
If you do the same trick with attr_reader/attr_writer, you can create
accessor functions for the variable. "23" and "23=" show up in the
methods() array. You can call them, but only using foo.send"23=",
42).

Indeed.


* parse.y (rb_intern): instance/class variables should not start with
a digit. [ruby-talk:94087]

Index: parse.y
===================================================================
RCS file: /cvs/ruby/src/ruby/parse.y,v
retrieving revision 1.316
diff -u -2 -p -r1.316 parse.y
--- parse.y 12 Feb 2004 06:23:24 -0000 1.316
+++ parse.y 3 Mar 2004 00:02:29 -0000
@@ -2457,4 +2457,5 @@ none : /* none */ {$$ = 0;}
# define SIGN_EXTEND_CHAR(c) ((((unsigned char)(c)) ^ 128) - 128)
#endif
+#define is_identfirst(c) (SIGN_EXTEND_CHAR(c)!=-1&&(ISALPHA(c) || (c) == '_' || ismbchar(c)))
#define is_identchar(c) (SIGN_EXTEND_CHAR(c)!=-1&&(ISALNUM(c) || (c) == '_' || ismbchar(c)))

@@ -3154,5 +3155,5 @@ heredoc_identifier()

default:
- if (!is_identchar(c)) {
+ if (!is_identfirst(c)) {
pushback(c);
if (func & STR_FUNC_INDENT) {
@@ -4269,5 +4270,5 @@ yylex()

default:
- if (!is_identchar(c)) {
+ if (!is_identfirst(c)) {
pushback(c);
return '$';
@@ -4294,5 +4295,5 @@ yylex()
}
}
- if (!is_identchar(c)) {
+ if (!is_identfirst(c)) {
pushback(c);
return '@';
@@ -4331,5 +4332,5 @@ yylex()
c = nextc();
} while (is_identchar(c));
- if ((c == '!' || c == '?') && is_identchar(tok()[0]) && !peek('=')) {
+ if ((c == '!' || c == '?') && is_identfirst(tok()[0]) && !peek('=')) {
tokadd(c);
}
@@ -5861,5 +5862,5 @@ rb_intern(name)
break;
default:
- if (name[0] != '_' && !ISALPHA(name[0]) && !ismbchar(name[0])) {
+ if (!is_identfirst(name[0])) {
/* operators */
int i;
@@ -5895,6 +5856,8 @@ rb_intern(name)
break;
}
- while (m <= name + last && is_identchar(*m)) {
- m += mbclen(*m);
+ if (m <= name + last && is_identfirst(*m)) {
+ do {
+ m += mbclen(*m);
+ } while (m <= name + last && is_identchar(*m));
}
if (*m) id = ID_JUNK;

 

[nobu.nokada]

Hi,

At Wed, 3 Mar 2004 09:15:28 +0900,

@@ -5861,5 +5862,5 @@ rb_intern(name)
break;
default:
- if (name[0] != '_' && !ISALPHA(name[0]) && !ismbchar(name[0])) {
+ if (!is_identfirst(name[0])) {
/* operators */
int i;
@@ -5895,6 +5856,8 @@ rb_intern(name)
break;
}
- while (m <= name + last && is_identchar(*m)) {
- m += mbclen(*m);
+ if (m <= name + last && is_identfirst(*m)) {
+ do {
+ m += mbclen(*m);
+ } while (m <= name + last && is_identchar(*m));
}
if (*m) id = ID_JUNK;

Sorry, wrong patch.

@@ -5859,7 +5860,8 @@ rb_intern(name)
}
m++;
+ if (!is_identfirst(*m)) id = ID_JUNK;
break;
default:
- if (name[0] != '_' && !ISALPHA(name[0]) && !ismbchar(name[0])) {
+ if (!is_identfirst(name[0])) {
/* operators */
int i;