concat

/*
 *  call-seq:
 *     str << fixnum        => str
 *     str.concat(fixnum)   => str
 *     str << obj           => str
 *     str.concat(obj)      => str
 *  
 *  Append---Concatenates the given object to <i>str</i>. If the object is a
 *  <code>Fixnum</code> between 0 and 255, it is converted to a character before
 *  concatenation.
 *     
 *     a = "hello "
 *     a << "world"   #=> "hello world"
 *     a.concat(33)   #=> "hello world!"
 */

VALUE
rb_str_concat(str1, str2)
    VALUE str1, str2;
{
    if (FIXNUM_P(str2)) {
        int i = FIX2INT(str2);
        if (0 <= i && i <= 0xff) { /* byte */
            char c = i;
            return rb_str_cat(str1, &c, 1);
        }
    }
    str1 = rb_str_append(str1, str2);

    return str1;
}