Class: Regexp

Inherits:
Object show all
Defined in:
re.c,
re.c

Overview

A Regexp holds a regular expression, used to match a pattern against strings. Regexps are created using the /.../ and %r{...} literals, and by the Regexp::new constructor.

:include: doc/regexp.rdoc

Constant Summary collapse

IGNORECASE =

see Regexp.options and Regexp.new

INT2FIX(ONIG_OPTION_IGNORECASE)
EXTENDED =

see Regexp.options and Regexp.new

INT2FIX(ONIG_OPTION_EXTEND)
MULTILINE =

see Regexp.options and Regexp.new

INT2FIX(ONIG_OPTION_MULTILINE)
FIXEDENCODING =

see Regexp.options and Regexp.new

INT2FIX(ARG_ENCODING_FIXED)
NOENCODING =

see Regexp.options and Regexp.new

INT2FIX(ARG_ENCODING_NONE)

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#new(string, [options]) ⇒ Regexp #new(regexp) ⇒ Regexp #compile(string, [options]) ⇒ Regexp #compile(regexp) ⇒ Regexp

Constructs a new regular expression from pattern, which can be either a String or a Regexp (in which case that regexp's options are propagated), and new options may not be specified (a change as of Ruby 1.8).

If options is an Integer, it should be one or more of the constants Regexp::EXTENDED, Regexp::IGNORECASE, and Regexp::MULTILINE, or-ed together. Otherwise, if options is not nil or false, the regexp will be case insensitive.

r1 = Regexp.new('^a-z+:\\s+\w+') #=> /^a-z+:\s+\w+/
r2 = Regexp.new('cat', true)     #=> /cat/i
r3 = Regexp.new(r2)              #=> /cat/i
r4 = Regexp.new('dog', Regexp::EXTENDED | Regexp::IGNORECASE) #=> /dog/ix

Overloads:

  • #new(string, [options]) ⇒ Regexp
  • #new(regexp) ⇒ Regexp
  • #compile(string, [options]) ⇒ Regexp
  • #compile(regexp) ⇒ Regexp

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# File 're.c', line 3440

static VALUE
rb_reg_initialize_m(int argc, VALUE *argv, VALUE self)
{
    int flags = 0;
    VALUE str;
    rb_encoding *enc = 0;

    rb_check_arity(argc, 1, 3);
    if (RB_TYPE_P(argv[0], T_REGEXP)) {
	VALUE re = argv[0];

	if (argc > 1) {
	    rb_warn("flags ignored");
	}
	rb_reg_check(re);
	flags = rb_reg_options(re);
	str = RREGEXP_SRC(re);
    }
    else {
	if (argc >= 2) {
	    if (FIXNUM_P(argv[1])) flags = FIX2INT(argv[1]);
	    else if (RTEST(argv[1])) flags = ONIG_OPTION_IGNORECASE;
	}
	if (argc == 3 && !NIL_P(argv[2])) {
	    char *kcode = StringValuePtr(argv[2]);
	    if (kcode[0] == 'n' || kcode[0] == 'N') {
		enc = rb_ascii8bit_encoding();
		flags |= ARG_ENCODING_NONE;
	    }
	    else {
                rb_category_warn(RB_WARN_CATEGORY_DEPRECATED, "encoding option is ignored - %s", kcode);
	    }
	}
	str = StringValue(argv[0]);
    }
    if (enc && rb_enc_get(str) != enc)
	rb_reg_init_str_enc(self, str, enc, flags);
    else
	rb_reg_init_str(self, str, flags);
    return self;
}

Class Method Details

.compileObject

Alias for Regexp.new

.escape(str) ⇒ String .quote(str) ⇒ String

Escapes any characters that would have special meaning in a regular expression. Returns a new escaped string with the same or compatible encoding. For any string, Regexp.new(Regexp.escape(str))=~str will be true.

Regexp.escape('\*?{}.')   #=> \\\*\?\{\}\.

Overloads:


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# File 're.c', line 3594

static VALUE
rb_reg_s_quote(VALUE c, VALUE str)
{
    return rb_reg_quote(reg_operand(str, TRUE));
}

.last_matchMatchData .last_match(n) ⇒ String

The first form returns the MatchData object generated by the last successful pattern match. Equivalent to reading the special global variable $~ (see Special global variables in Regexp for details).

The second form returns the nth field in this MatchData object. n can be a string or symbol to reference a named capture.

Note that the last_match is local to the thread and method scope of the method that did the pattern match.

/c(.)t/ =~ 'cat'        #=> 0
Regexp.last_match       #=> #<MatchData "cat" 1:"a">
Regexp.last_match(0)    #=> "cat"
Regexp.last_match(1)    #=> "a"
Regexp.last_match(2)    #=> nil

/(?<lhs>\w+)\s*=\s*(?<rhs>\w+)/ =~ "var = val"
Regexp.last_match       #=> #<MatchData "var = val" lhs:"var" rhs:"val">
Regexp.last_match(:lhs) #=> "var"
Regexp.last_match(:rhs) #=> "val"

Overloads:


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# File 're.c', line 3988

static VALUE
rb_reg_s_last_match(int argc, VALUE *argv, VALUE _)
{
    if (rb_check_arity(argc, 0, 1) == 1) {
        VALUE match = rb_backref_get();
        int n;
        if (NIL_P(match)) return Qnil;
        n = match_backref_number(match, argv[0]);
	return rb_reg_nth_match(n, match);
    }
    return match_getter();
}

.escape(str) ⇒ String .quote(str) ⇒ String

Escapes any characters that would have special meaning in a regular expression. Returns a new escaped string with the same or compatible encoding. For any string, Regexp.new(Regexp.escape(str))=~str will be true.

Regexp.escape('\*?{}.')   #=> \\\*\?\{\}\.

Overloads:


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# File 're.c', line 3594

static VALUE
rb_reg_s_quote(VALUE c, VALUE str)
{
    return rb_reg_quote(reg_operand(str, TRUE));
}

.try_convert(obj) ⇒ nil

Try to convert obj into a Regexp, using to_regexp method. Returns converted regexp or nil if obj cannot be converted for any reason.

Regexp.try_convert(/re/)         #=> /re/
Regexp.try_convert("re")         #=> nil

o = Object.new
Regexp.try_convert(o)            #=> nil
def o.to_regexp() /foo/ end
Regexp.try_convert(o)            #=> /foo/

Returns:

  • (nil)

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# File 're.c', line 3635

static VALUE
rb_reg_s_try_convert(VALUE dummy, VALUE re)
{
    return rb_check_regexp_type(re);
}

.union(pat1, pat2, ...) ⇒ Regexp .union(pats_ary) ⇒ Regexp

Return a Regexp object that is the union of the given patterns, i.e., will match any of its parts. The patterns can be Regexp objects, in which case their options will be preserved, or Strings. If no patterns are given, returns /(?!)/. The behavior is unspecified if any given pattern contains capture.

Regexp.union                         #=> /(?!)/
Regexp.union("penzance")             #=> /penzance/
Regexp.union("a+b*c")                #=> /a\+b\*c/
Regexp.union("skiing", "sledding")   #=> /skiing|sledding/
Regexp.union(["skiing", "sledding"]) #=> /skiing|sledding/
Regexp.union(/dogs/, /cats/i)        #=> /(?-mix:dogs)|(?i-mx:cats)/

Note: the arguments for ::union will try to be converted into a regular expression literal via #to_regexp.

Overloads:


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# File 're.c', line 3777

static VALUE
rb_reg_s_union_m(VALUE self, VALUE args)
{
    VALUE v;
    if (RARRAY_LEN(args) == 1 &&
        !NIL_P(v = rb_check_array_type(rb_ary_entry(args, 0)))) {
        return rb_reg_s_union(self, v);
    }
    return rb_reg_s_union(self, args);
}

Instance Method Details

#==(other_rxp) ⇒ Boolean #eql?(other_rxp) ⇒ Boolean

Equality—Two regexps are equal if their patterns are identical, they have the same character set code, and their casefold? values are the same.

/abc/  == /abc/x   #=> false
/abc/  == /abc/i   #=> false
/abc/  == /abc/u   #=> false
/abc/u == /abc/n   #=> false

Overloads:

  • #==(other_rxp) ⇒ Boolean

    Returns:

    • (Boolean)
  • #eql?(other_rxp) ⇒ Boolean

    Returns:

    • (Boolean)

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# File 're.c', line 3045

static VALUE
rb_reg_equal(VALUE re1, VALUE re2)
{
    if (re1 == re2) return Qtrue;
    if (!RB_TYPE_P(re2, T_REGEXP)) return Qfalse;
    rb_reg_check(re1); rb_reg_check(re2);
    if (FL_TEST(re1, KCODE_FIXED) != FL_TEST(re2, KCODE_FIXED)) return Qfalse;
    if (RREGEXP_PTR(re1)->options != RREGEXP_PTR(re2)->options) return Qfalse;
    if (RREGEXP_SRC_LEN(re1) != RREGEXP_SRC_LEN(re2)) return Qfalse;
    if (ENCODING_GET(re1) != ENCODING_GET(re2)) return Qfalse;
    if (memcmp(RREGEXP_SRC_PTR(re1), RREGEXP_SRC_PTR(re2), RREGEXP_SRC_LEN(re1)) == 0) {
	return Qtrue;
    }
    return Qfalse;
}

#===(str) ⇒ Boolean

Case Equality—Used in case statements.

a = "HELLO"
case a
when /\A[a-z]*\z/; print "Lower case\n"
when /\A[A-Z]*\z/; print "Upper case\n"
else;              print "Mixed case\n"
end
#=> "Upper case"

Following a regular expression literal with the #=== operator allows you to compare against a String.

/^[a-z]*$/ === “HELLO” #=> false /^[A-Z]*$/ === “HELLO” #=> true

Returns:

  • (Boolean)

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# File 're.c', line 3230

VALUE
rb_reg_eqq(VALUE re, VALUE str)
{
    long start;

    str = reg_operand(str, FALSE);
    if (NIL_P(str)) {
	rb_backref_set(Qnil);
	return Qfalse;
    }
    start = rb_reg_search(re, str, 0, 0);
    if (start < 0) {
	return Qfalse;
    }
    return Qtrue;
}

#=~(str) ⇒ Integer?

Match—Matches rxp against str.

/at/ =~ "input data"   #=> 7
/ax/ =~ "input data"   #=> nil

If =~ is used with a regexp literal with named captures, captured strings (or nil) is assigned to local variables named by the capture names.

/(?<lhs>\w+)\s*=\s*(?<rhs>\w+)/ =~ "  x = y  "
p lhs    #=> "x"
p rhs    #=> "y"

If it is not matched, nil is assigned for the variables.

/(?<lhs>\w+)\s*=\s*(?<rhs>\w+)/ =~ "  x = "
p lhs    #=> nil
p rhs    #=> nil

This assignment is implemented in the Ruby parser. The parser detects 'regexp-literal =~ expression' for the assignment. The regexp must be a literal without interpolation and placed at left hand side.

The assignment does not occur if the regexp is not a literal.

re = /(?<lhs>\w+)\s*=\s*(?<rhs>\w+)/
re =~ "  x = y  "
p lhs    # undefined local variable
p rhs    # undefined local variable

A regexp interpolation, #{}, also disables the assignment.

rhs_pat = /(?<rhs>\w+)/
/(?<lhs>\w+)\s*=\s*#{rhs_pat}/ =~ "x = y"
p lhs    # undefined local variable

The assignment does not occur if the regexp is placed at the right hand side.

"  x = y  " =~ /(?<lhs>\w+)\s*=\s*(?<rhs>\w+)/
p lhs, rhs # undefined local variable

Returns:


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# File 're.c', line 3200

VALUE
rb_reg_match(VALUE re, VALUE str)
{
    long pos = reg_match_pos(re, &str, 0);
    if (pos < 0) return Qnil;
    pos = rb_str_sublen(str, pos);
    return LONG2FIX(pos);
}

#casefold?Boolean

Returns the value of the case-insensitive flag.

/a/.casefold?           #=> false
/a/i.casefold?          #=> true
/(?i:a)/.casefold?      #=> false

Returns:

  • (Boolean)

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# File 're.c', line 723

static VALUE
rb_reg_casefold_p(VALUE re)
{
    rb_reg_check(re);
    if (RREGEXP_PTR(re)->options & ONIG_OPTION_IGNORECASE) return Qtrue;
    return Qfalse;
}

#encodingEncoding

Returns the Encoding object that represents the encoding of obj.

Returns:


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# File 'encoding.c', line 1201

VALUE
rb_obj_encoding(VALUE obj)
{
    int idx = rb_enc_get_index(obj);
    if (idx < 0) {
	rb_raise(rb_eTypeError, "unknown encoding");
    }
    return rb_enc_from_encoding_index(idx & ENC_INDEX_MASK);
}

#==(other_rxp) ⇒ Boolean #eql?(other_rxp) ⇒ Boolean

Equality—Two regexps are equal if their patterns are identical, they have the same character set code, and their casefold? values are the same.

/abc/  == /abc/x   #=> false
/abc/  == /abc/i   #=> false
/abc/  == /abc/u   #=> false
/abc/u == /abc/n   #=> false

Overloads:

  • #==(other_rxp) ⇒ Boolean

    Returns:

    • (Boolean)
  • #eql?(other_rxp) ⇒ Boolean

    Returns:

    • (Boolean)

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# File 're.c', line 3045

static VALUE
rb_reg_equal(VALUE re1, VALUE re2)
{
    if (re1 == re2) return Qtrue;
    if (!RB_TYPE_P(re2, T_REGEXP)) return Qfalse;
    rb_reg_check(re1); rb_reg_check(re2);
    if (FL_TEST(re1, KCODE_FIXED) != FL_TEST(re2, KCODE_FIXED)) return Qfalse;
    if (RREGEXP_PTR(re1)->options != RREGEXP_PTR(re2)->options) return Qfalse;
    if (RREGEXP_SRC_LEN(re1) != RREGEXP_SRC_LEN(re2)) return Qfalse;
    if (ENCODING_GET(re1) != ENCODING_GET(re2)) return Qfalse;
    if (memcmp(RREGEXP_SRC_PTR(re1), RREGEXP_SRC_PTR(re2), RREGEXP_SRC_LEN(re1)) == 0) {
	return Qtrue;
    }
    return Qfalse;
}

#fixed_encoding?Boolean

Returns false if rxp is applicable to a string with any ASCII compatible encoding. Returns true otherwise.

r = /a/
r.fixed_encoding?                               #=> false
r =~ "\u{6666} a"                               #=> 2
r =~ "\xa1\xa2 a".force_encoding("euc-jp")      #=> 2
r =~ "abc".force_encoding("euc-jp")             #=> 0

r = /a/u
r.fixed_encoding?                               #=> true
r.encoding                                      #=> #<Encoding:UTF-8>
r =~ "\u{6666} a"                               #=> 2
r =~ "\xa1\xa2".force_encoding("euc-jp")        #=> Encoding::CompatibilityError
r =~ "abc".force_encoding("euc-jp")             #=> 0

r = /\u{6666}/
r.fixed_encoding?                               #=> true
r.encoding                                      #=> #<Encoding:UTF-8>
r =~ "\u{6666} a"                               #=> 0
r =~ "\xa1\xa2".force_encoding("euc-jp")        #=> Encoding::CompatibilityError
r =~ "abc".force_encoding("euc-jp")             #=> nil

Returns:

  • (Boolean)

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# File 're.c', line 1389

static VALUE
rb_reg_fixed_encoding_p(VALUE re)
{
    if (FL_TEST(re, KCODE_FIXED))
        return Qtrue;
    else
        return Qfalse;
}

#hashInteger

Produce a hash based on the text and options of this regular expression.

See also Object#hash.

Returns:


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# File 're.c', line 3011

static VALUE
rb_reg_hash(VALUE re)
{
    st_index_t hashval = reg_hash(re);
    return ST2FIX(hashval);
}

#initialize_copy(re) ⇒ Object

:nodoc:


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# File 're.c', line 3789

static VALUE
rb_reg_init_copy(VALUE copy, VALUE re)
{
    if (!OBJ_INIT_COPY(copy, re)) return copy;
    rb_reg_check(re);
    return rb_reg_init_str(copy, RREGEXP_SRC(re), rb_reg_options(re));
}

#inspectString

Produce a nicely formatted string-version of rxp. Perhaps surprisingly, #inspect actually produces the more natural version of the string than #to_s.

/ab+c/ix.inspect        #=> "/ab+c/ix"

Returns:


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# File 're.c', line 515

static VALUE
rb_reg_inspect(VALUE re)
{
    if (!RREGEXP_PTR(re) || !RREGEXP_SRC(re) || !RREGEXP_SRC_PTR(re)) {
        return rb_any_to_s(re);
    }
    return rb_reg_desc(RREGEXP_SRC_PTR(re), RREGEXP_SRC_LEN(re), re);
}

#match(str, pos = 0) ⇒ MatchData? #match(str, pos = 0) {|match| ... } ⇒ Object

Returns a MatchData object describing the match, or nil if there was no match. This is equivalent to retrieving the value of the special variable $~ following a normal match. If the second parameter is present, it specifies the position in the string to begin the search.

/(.)(.)(.)/.match("abc")[2]   #=> "b"
/(.)(.)/.match("abc", 1)[2]   #=> "c"

If a block is given, invoke the block with MatchData if match succeed, so that you can write

/M(.*)/.match("Matz") do |m|
  puts m[0]
  puts m[1]
end

instead of

if m = /M(.*)/.match("Matz")
  puts m[0]
  puts m[1]
end

The return value is a value from block execution in this case.

Overloads:


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# File 're.c', line 3311

static VALUE
rb_reg_match_m(int argc, VALUE *argv, VALUE re)
{
    VALUE result, str, initpos;
    long pos;

    if (rb_scan_args(argc, argv, "11", &str, &initpos) == 2) {
	pos = NUM2LONG(initpos);
    }
    else {
	pos = 0;
    }

    pos = reg_match_pos(re, &str, pos);
    if (pos < 0) {
	rb_backref_set(Qnil);
	return Qnil;
    }
    result = rb_backref_get();
    rb_match_busy(result);
    if (!NIL_P(result) && rb_block_given_p()) {
	return rb_yield(result);
    }
    return result;
}

#match?(str) ⇒ Boolean #match?(str, pos) ⇒ Boolean

Returns a true or false indicates whether the regexp is matched or not without updating $~ and other related variables. If the second parameter is present, it specifies the position in the string to begin the search.

/R.../.match?("Ruby")    #=> true
/R.../.match?("Ruby", 1) #=> false
/P.../.match?("Ruby")    #=> false
$&                       #=> nil

Overloads:

  • #match?(str) ⇒ Boolean

    Returns:

    • (Boolean)
  • #match?(str, pos) ⇒ Boolean

    Returns:

    • (Boolean)

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# File 're.c', line 3353

static VALUE
rb_reg_match_m_p(int argc, VALUE *argv, VALUE re)
{
    long pos = rb_check_arity(argc, 1, 2) > 1 ? NUM2LONG(argv[1]) : 0;
    return rb_reg_match_p(re, argv[0], pos);
}

#named_capturesHash

Returns a hash representing information about named captures of rxp.

A key of the hash is a name of the named captures. A value of the hash is an array which is list of indexes of corresponding named captures.

/(?<foo>.)(?<bar>.)/.named_captures
#=> {"foo"=>[1], "bar"=>[2]}

/(?<foo>.)(?<foo>.)/.named_captures
#=> {"foo"=>[1, 2]}

If there are no named captures, an empty hash is returned.

/(.)(.)/.named_captures
#=> {}

Returns:


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# File 're.c', line 835

static VALUE
rb_reg_named_captures(VALUE re)
{
    regex_t *reg = (rb_reg_check(re), RREGEXP_PTR(re));
    VALUE hash = rb_hash_new_with_size(onig_number_of_names(reg));
    onig_foreach_name(reg, reg_named_captures_iter, (void*)hash);
    return hash;
}

#namesArray

Returns a list of names of captures as an array of strings.

/(?<foo>.)(?<bar>.)(?<baz>.)/.names
#=> ["foo", "bar", "baz"]

/(?<foo>.)(?<foo>.)/.names
#=> ["foo"]

/(.)(.)/.names
#=> []

Returns:


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# File 're.c', line 787

static VALUE
rb_reg_names(VALUE re)
{
    VALUE ary;
    rb_reg_check(re);
    ary = rb_ary_new_capa(onig_number_of_names(RREGEXP_PTR(re)));
    onig_foreach_name(RREGEXP_PTR(re), reg_names_iter, (void*)ary);
    return ary;
}

#optionsInteger

Returns the set of bits corresponding to the options used when creating this Regexp (see Regexp::new for details. Note that additional bits may be set in the returned options: these are used internally by the regular expression code. These extra bits are ignored if the options are passed to Regexp::new.

Regexp::IGNORECASE                  #=> 1
Regexp::EXTENDED                    #=> 2
Regexp::MULTILINE                   #=> 4

/cat/.options                       #=> 0
/cat/ix.options                     #=> 3
Regexp.new('cat', true).options     #=> 1
/\xa1\xa2/e.options                 #=> 16

r = /cat/ix
Regexp.new(r.source, r.options)     #=> /cat/ix

Returns:


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# File 're.c', line 755

static VALUE
rb_reg_options_m(VALUE re)
{
    int options = rb_reg_options(re);
    return INT2NUM(options);
}

#sourceString

Returns the original string of the pattern.

/ab+c/ix.source #=> "ab+c"

Note that escape sequences are retained as is.

/\x20\+/.source  #=> "\\x20\\+"

Returns:


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# File 're.c', line 493

static VALUE
rb_reg_source(VALUE re)
{
    VALUE str;

    rb_reg_check(re);
    str = rb_str_dup(RREGEXP_SRC(re));
    return str;
}

#to_sString

Returns a string containing the regular expression and its options (using the (?opts:source) notation. This string can be fed back in to Regexp::new to a regular expression with the same semantics as the original. (However, Regexp#== may not return true when comparing the two, as the source of the regular expression itself may differ, as the example shows). Regexp#inspect produces a generally more readable version of rxp.

r1 = /ab+c/ix           #=> /ab+c/ix
s1 = r1.to_s            #=> "(?ix-m:ab+c)"
r2 = Regexp.new(s1)     #=> /(?ix-m:ab+c)/
r1 == r2                #=> false
r1.source               #=> "ab+c"
r2.source               #=> "(?ix-m:ab+c)"

Returns:


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# File 're.c', line 546

static VALUE
rb_reg_to_s(VALUE re)
{
    return rb_reg_str_with_term(re, '/');
}

#~(rxp) ⇒ Integer?

Match—Matches rxp against the contents of $_. Equivalent to rxp =~ $_.

$_ = "input data"
~ /at/   #=> 7

Returns:


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# File 're.c', line 3259

VALUE
rb_reg_match2(VALUE re)
{
    long start;
    VALUE line = rb_lastline_get();

    if (!RB_TYPE_P(line, T_STRING)) {
	rb_backref_set(Qnil);
	return Qnil;
    }

    start = rb_reg_search(re, line, 0, 0);
    if (start < 0) {
	return Qnil;
    }
    start = rb_str_sublen(line, start);
    return LONG2FIX(start);
}