DaniWeb Forum Index > Software Development > C++

C++ RSS

.rfind for Managed

Please support our C++ advertiser: Intel Parallel Studio Home

Thread Solved

•

Join Date: Feb 2008

Posts: 517

Reputation: Jennifer84 is an unknown quantity at this point

Solved Threads: 1

Jennifer84 Jennifer84 is offline

Offline

Posting Pro

.rfind for Managed

Sep 30th, 2008

I am using this in the std:: to check for the first occurance of " " backwards (rfind).
If I go managed .NET, I wonder if there is any simular method for this
using str->

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
std::string::size_type index2 = str.rfind(" ", index - 1);
std::string::size_type index2 = str.rfind(" ", index - 1);

•

Join Date: Sep 2004

Posts: 7,630

Reputation: Narue has a reputation beyond repute

Solved Threads: 718

Narue

Offline

Code Goddess

Re: .rfind for Managed

Sep 30th, 2008

Presumably by go managed .NET you mean use the String class instead of std::string. If so, the LastIndexOf method is what you're looking for.

On a side note, do you even know that MSDN exists, or are you using the people on Daniweb as your personal programming reference?

I'm here to prove you wrong.

•

Join Date: Feb 2008

Posts: 517

Reputation: Jennifer84 is an unknown quantity at this point

Solved Threads: 1

Jennifer84 Jennifer84 is offline

Offline

Posting Pro

Re: .rfind for Managed

Sep 30th, 2008

Yes I know that MSDN exists but often the examples and info are not so clear there.
I did look up all members for the String^ before and also found LastIndexOf but as I understand this does not have the same function as .rfind.

LastIndexOf(MSDN):
Reports the index position of the last occurrence of a specified Unicode character or String within this instance.
So If you will find the first " " by looking backwards in a string with a startindex: 3 with .rfind, it will look like this:

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
std::string str;
str = "1 23 56"
int index = str.rfind(" ", 3); //index should return 1
std::string str;
str = "1 23 56"
int index = str.rfind(" ", 3); //index should return 1

If you will use LastIndexOf you are looking from the beginning of the string and not backwards.
So index will return: 2 here.

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
String^ tot = "1 23 56; 
 
int index = 0;
index = tot->LastIndexOf(" "); //Returns 4
 
String^ tot = "1 23 56; 
		 
int index = 0;
index = tot->LastIndexOf(" "); //Returns 4

•

Originally Posted by Narue

Presumably by go managed .NET you mean use the String class instead of std::string. If so, the LastIndexOf method is what you're looking for.

On a side note, do you even know that MSDN exists, or are you using the people on Daniweb as your personal programming reference?

Last edited by Jennifer84; Sep 30th, 2008 at 3:49 pm.

•

Join Date: Sep 2004

Posts: 7,630

Reputation: Narue has a reputation beyond repute

Solved Threads: 718

Narue

Offline

Code Goddess

Re: .rfind for Managed

Sep 30th, 2008

>as I understand this does not have the same function as .rfind.
Yes, yes it does.

>int index = str.rfind(" ", 3); //index should return 1
Correct.

>index = tot->LastIndexOf(" "); //Returns 4
Correct, but this isn't an equivalent call to the rfind call you compared with. If you use the overload of LastIndexOf that takes a starting index, and make that starting index 3, you'll find that it returns 1 as well:

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
#include <iostream>
#include <string>
 
using namespace System;
 
int main()
{
  std::string s1 = "1 23 56";
  String^ s2 = "1 23 56"; 
 
  Console::WriteLine( s1.rfind ( " ", 3 ) );
  Console::WriteLine( s2->LastIndexOf ( " ", 3 ) );
}
#include <iostream>
#include <string>

using namespace System;

int main()
{
  std::string s1 = "1 23 56";
  String^ s2 = "1 23 56"; 
  
  Console::WriteLine( s1.rfind ( " ", 3 ) );
  Console::WriteLine( s2->LastIndexOf ( " ", 3 ) );
}

>If you will use LastIndexOf you are looking from the beginning of the string and not backwards.
I fail to see how you could think that when the documentation explicitly says this (for String::LastIndexOf(String)):

•

The search begins at the last character position of this instance and proceeds backward toward the beginning until either value is found or the first character position has been examined.

And this (for String::LastIndexOf(String, Int32)):

•

The search begins at the startIndex character position of this instance and proceeds backward toward the beginning until either value is found or the first character position has been examined. For example, if startIndex is Length - 1, the method searches every character from the last character in the string to the beginning.

I'm here to prove you wrong.

•

Join Date: Feb 2008

Posts: 517

Reputation: Jennifer84 is an unknown quantity at this point

Solved Threads: 1

Jennifer84 Jennifer84 is offline

Offline

Posting Pro

Re: .rfind for Managed

Sep 30th, 2008

Yes it did look backwards

, I didn´t think it did. I red about LastIndexOf here
I couldn´t find here where it described..
>> The search begins at the last character position of this instance and proceeds backward..

This helped great, Thank you !

Last edited by Jennifer84; Sep 30th, 2008 at 6:19 pm.