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Feature #3675

closed

String#prepend, String#>>

Feature #3675: String#prepend, String#>>

Added by sorah (Sorah Fukumori) about 16 years ago. Updated over 15 years ago.

Status:
Closed
Assignee:
matz (Yukihiro Matsumoto)
[ruby-dev:41969]

Description

=begin
sorahです.

通常, Stringでの文字列を手前に破壊的に加えるのは, a = "foo" + a 等で行いますが,
直感で読みにくく, 記号などで書きにくくなっていると思います.

なので, String#prependと String#>> を追加するというのはどうでしょうか.

それぞれ以下のように機能します.

a = "bar"
a.prepend("foo") #=> "foobar"
p a #=> "foobar"

b = "bar"
"foo" >> b #=> "foobar"
p b #=> "foobar"

patchはこちらです (git diff --no-prefixにて生成):

diff --git string.c string.c
index 0aa2e6c..6c9be57 100644
--- string.c
+++ string.c
@@ -2055,6 +2055,43 @@ rb_str_concat(VALUE str1, VALUE str2)
}
}

+/*

    • call-seq:
    • str.prepend(other_str)  -> str
    • Prepend---Prepend the given string to str.
    • a = "world"
    • a.prepend("hello ") #=> "hello world"
    • a #=> "hello world"
  • */

+static VALUE
+rb_str_prepend(VALUE str, VALUE str2)
+{

  • StringValue(str2);
  • StringValue(str);
  • rb_str_update(str, 0L, 0L, str2);
  • return str;
    +}

+/*

    • call-seq:
    • str >> other_str -> other_str
    • Prepend---Prepend self string to other_str.
    • a = "world"
    • "hello " >> a #=> "hello world"
    • a #=> "hello world"
  • */

+static VALUE
+rb_str_prepend_to_another(VALUE str1, VALUE str2)
+{

  • return rb_str_prepend(str2, str1);
    +}

st_index_t
rb_memhash(const void *ptr, long len)
{
@@ -7524,6 +7561,8 @@ Init_String(void)
rb_define_method(rb_cString, "reverse!", rb_str_reverse_bang, 0);
rb_define_method(rb_cString, "concat", rb_str_concat, 1);
rb_define_method(rb_cString, "<<", rb_str_concat, 1);

  • rb_define_method(rb_cString, "prepend", rb_str_prepend, 1);
  • rb_define_method(rb_cString, ">>", rb_str_prepend_to_another, 1);
    rb_define_method(rb_cString, "crypt", rb_str_crypt, 1);
    rb_define_method(rb_cString, "intern", rb_str_intern, 0);
    rb_define_method(rb_cString, "to_sym", rb_str_intern, 0);
    diff --git test/ruby/test_string.rb test/ruby/test_string.rb
    index 02271ce..da2477f 100644
    --- test/ruby/test_string.rb
    +++ test/ruby/test_string.rb
    @@ -1882,4 +1882,36 @@ class TestString < Test::Unit::TestCase
    assert_equal('"\u3042\u3044\u3046"', "\u3042\u3044\u3046".encode(e).inspect)
    end
    end
  • def test_prepend_to_another
  • assert_equal(S("hello world"), "hello " >> "world")
  • foo = Object.new
  • def foo.to_str
  •  "b"
  • end
  • assert_equal(S("ab"), "a" >> foo)
  • a = S("world!")
  • b = S("hello ")
  • b >> a
  • assert_equal(S("hello world!"), a)
  • assert_equal(S("hello "), b)
  • end
  • def test_prepend
  • assert_equal(S("hello world!"), "world!".prepend("hello "))
  • foo = Object.new
  • def foo.to_str
  •  "b"
  • end
  • assert_equal(S("ba"), "a".prepend(foo))
  • a = S("world")
  • b = S("hello ")
  • a.prepend(b)
  • assert_equal(S("hello world"), a)
  • assert_equal(S("hello "), b)
  • end
    end
    =end
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