Implement String#chr

mrbgems/mruby-string-ext/src/string.c

@@ -175,6 +175,21 @@ mrb_str_oct(mrb_state *mrb, mrb_value self)
   return mrb_str_to_inum(mrb, self, 8, FALSE);
 }
 
+/*
+ *  call-seq:
+ *     string.chr    ->  string
+ *
+ *  Returns a one-character string at the beginning of the string.
+ *
+ *     a = "abcde"
+ *     a.chr    #=> "a"
+ */
+static mrb_value
+mrb_str_chr(mrb_state *mrb, mrb_value self)
+{
+  return mrb_str_substr(mrb, self, 0, 1);
+}
+
 void
 mrb_mruby_string_ext_gem_init(mrb_state* mrb)
 {
@@ -190,6 +205,7 @@ mrb_mruby_string_ext_gem_init(mrb_state* mrb)
   mrb_define_method(mrb, s, "end_with?",       mrb_str_end_with,        MRB_ARGS_REST());
   mrb_define_method(mrb, s, "hex",             mrb_str_hex,             MRB_ARGS_NONE());
   mrb_define_method(mrb, s, "oct",             mrb_str_oct,             MRB_ARGS_NONE());
+  mrb_define_method(mrb, s, "chr",             mrb_str_chr,             MRB_ARGS_NONE());
 }
 
 void

mrbgems/mruby-string-ext/test/string.rb

@@ -161,3 +161,7 @@ assert('String#oct') do
   assert_equal 8, "010".oct
   assert_equal (-8), "-10".oct
 end
+
+assert('String#chr') do
+  assert_equal "a", "abcde".chr
+end