A new class -->String

[jinheking]

String opAssign(wchar[] value) {
   int size = value.length;
   offset = 0;
   count = size;
   value = value;
   return this;
    }

That is this funcation!

"Frits van Bommel" <fvbommel at REMwOVExCAPSs.nl> дÈëÏûÏ¢ÐÂÎÅ:euvo53$3rg$1 at digitalmars.com...
> jinheking wrote:
>> I want to make a Class like java's String Class.
>> module jdk2d.lang;
>>
>> import std.stdio;
>> /*
>> * The <code>String</code> class represents character strings. All
>> * string literals in D programs, such as <code>"abc"</code>, are
>> * implemented as instances of this class.
>
> I don't think last bit is going to happen.
>
>> * @author  Caoqi
>> * @version 0.001, 07/03/30
>> * @since   JDK2D 0.02
>> * @url     http://jinheking.javaeye.com/admin
>> * <p>
>> */
>>
>> public class  String{
>>   private final wchar[] value;
>>
>>   /** The offset is the first index of the storage that is used. */
>>   private final int offset;
>>
>>   /** The count is the number of characters in the String. */
>>   private final int count;
>
> Those last two are unnecessary. wchar[] + slicing takes care of 
> everything.
> So all you need is
> private final wchar[] value;
> (and when the new constness proposal comes through, add const (or better 
> yet, invariant) to that)
>
>>   /*
>>    * Initializes a newly created {@code String} object so that it 
>> represents
>>    * an empty character sequence.  Note that use of this constructor is
>>    * unnecessary since Strings are immutable.
>>    */
>>   this(){
>>    this.offset = 0;
>>    this.count = 0;
>>    this.value = new wchar[0];
>
> just
> this.value = null;
> will do just fine.
>
>>   }
>>
>>   String opAssign(wchar[] value) {
>>    int size = value.length;
>>    offset = 0;
>>    count = size;
>>    value = value;
>>    return this;
>
> (You forgot a 'this' in front of the left-hand 'value' in that assignment)
>
> this.value = value.dup;
> To be sure the code outside can't modify the contents.
> Once constness comes through, add an overload that takes an invariant 
> wchar[] and doesn't dup.
>
>>     }
>>
>>   /*
>>      * Allocates a new {@code String} so that it represents the sequence 
>> of
>>      * characters currently contained in the character array argument. 
>> The
>>      * contents of the character array are copied; subsequent 
>> modification of
>>      * the character array does not affect the newly created string.
>>      *
>>      * @param  value
>>      *         The initial value of the string
>>      */
>>     public this(wchar[] value) {
>>    int size = value.length;
>>    this.offset = 0;
>>    this.count = size;
>>    this.value = value;
>
> Same as above:
> this.value = value.dup;
>
>>     }
>>
>>   /**
>>      * Returns the length of this string.
>>      * The length is equal to the number of <a 
>> href="Character.html#unicode">Unicode
>>      * code units</a> in the string.
>>      *
>>      * @return  the length of the sequence of characters represented by 
>> this
>>      *          object.
>>      */
>>     public int length() {
>>         return count;
>
> return value.length;
>
>>     }
>>
>>     /**
>>      * Returns <tt>true</tt> if, and only if, {@link #length()} is 
>> <tt>0</tt>.
>>      *
>>      * @return <tt>true</tt> if {@link #length()} is <tt>0</tt>, 
>> otherwise
>>      * <tt>false</tt>
>>      *
>>      * @since JDK2D 0.01
>>      */
>>     public bool isEmpty() {
>>     return count == 0;
>
> return value.length == 0;
>
>>     }
>>   /**
>>      * Returns the index within this string of the first occurrence of 
>> the
>>      * specified substring. The integer returned is the smallest value
>>      * <i>k</i> such that:
>>      * <blockquote><pre>
>>      * this.startsWith(str, <i>k</i>)
>>      * </pre></blockquote>
>>      * is <code>true</code>.
>>      *
>>      * @param   str   any string.
>>      * @return  if the string argument occurs as a substring within this
>>      *          object, then the index of the first character of the 
>> first
>>      *          such substring is returned; if it does not occur as a
>>      *          substring, <code>-1</code> is returned.
>>      */
>>
>>     public int indexOf(String str) {
>>    return indexOf(str, 0);
>>     }
>>
>>     public int indexOf(wchar[] str) {
>>    return indexOf(str, 0);
>>     }
>>
>>     /**
>>      * Returns the index within this string of the first occurrence of 
>> the
>>      * specified substring, starting at the specified index.  The integer
>>      * returned is the smallest value <tt>k</tt> for which:
>>      * <blockquote><pre>
>>      *     k &gt;= Math.min(fromIndex, this.length()) && 
>> this.startsWith(str, k)
>>      * </pre></blockquote>
>>      * If no such value of <i>k</i> exists, then -1 is returned.
>>      *
>>      * @param   str         the substring for which to search.
>>      * @param   fromIndex   the index from which to start the search.
>>      * @return  the index within this string of the first occurrence of 
>> the
>>      *          specified substring, starting at the specified index.
>>      */
>>     public int indexOf(String str, int fromIndex) {
>>         return indexOf(value, offset, count,
>>                        str.value, str.offset, str.count, fromIndex);
>>     }
>>
>>     public int indexOf(wchar[] wstr, int fromIndex) {
>>        String str=new String(wstr);
>>         return indexOf(value, offset, count,
>>                        str.value, str.offset, str.count, fromIndex);
>>     }
>>
>>     /**
>>      * Code shared by String and StringBuffer to do searches. The
>>      * source is the character array being searched, and the target
>>      * is the string being searched for.
>>      *
>>      * @param   source       the characters being searched.
>>      * @param   sourceOffset offset of the source string.
>>      * @param   sourceCount  count of the source string.
>>      * @param   target       the characters being searched for.
>>      * @param   targetOffset offset of the target string.
>>      * @param   targetCount  count of the target string.
>>      * @param   fromIndex    the index to begin searching from.
>>      */
>>     static int indexOf(wchar[] source, int sourceOffset, int sourceCount,
>>                        wchar[] target, int targetOffset, int targetCount,
>>                        int fromIndex) {
>>    if (fromIndex >= sourceCount) {
>>               return (targetCount == 0 ? sourceCount : -1);
>>    }
>>        if (fromIndex < 0) {
>>            fromIndex = 0;
>>        }
>>    if (targetCount == 0) {
>>        return fromIndex;
>>    }
>>
>>           wchar first  = target[targetOffset];
>>           int max = sourceOffset + (sourceCount - targetCount);
>>
>>           for (int i = sourceOffset + fromIndex; i <= max; i++) {
>>               /* Look for first character. */
>>               if (source[i] != first) {
>>                 i++;
>>                   while (i <= max && source[i] != first){
>>                    i++;
>>                   }
>>               }
>>
>>               /* Found first character, now look at the rest of v2 */
>>               if (i <= max) {
>>                   int j = i + 1;
>>                   int end = j + targetCount - 1;
>>                   for (int k = targetOffset + 1; j < end && (source[j] == 
>> target[k]);j++){
>>                     k++;
>>                   }
>>
>>                   if (j == end) {
>>                       /* Found whole string. */
>>                       return i - sourceOffset;
>>                   }
>>               }
>>           }
>>           return -1;
>>       }
>
> Using slicing so offset and counts don't need to be passed will allow you 
> to implement these more cleanly, I think.
>
>>
>>  char[] toString(){
>>   return cast(char[])std.utf.toUTF8(this.value);
>
> This is broken for your implementation but just fine for mine. (It doesn't 
> work for substrings in yours, it'll convert the entire string instead of 
> just the part this String object represents)
>
>>  }
>> }
>>
>> public static void  main() {
>>    String str = new String("The quick brown fox jumped over the lazy 
>> dog.");
>>    String s1 = new String("abc");
>>    s1="abc";
>>    writefln(s1);
>>    printf("%d\n",str.indexOf("z"));
>>    printf("%d\n",str.isEmpty());
>> }
>
> As a final note, there's a (less Java-like) string class implementation at 
> http://www.dprogramming.com/dstring.php. It stores its data as char[], 
> wchar[] or dchar[] and tries to use whichever is the most space-efficient 
> yet can still store all elements in a single array element. The last bit 
> allows it to implement "intuitive" slicing, never slicing in the middle of 
> a group of UTF-8 or UTF-16 code units that form a single character point 
> (if I got the terminology right).