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.rfind for Managed

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.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->

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std::string::size_type index2 = str.rfind(" ", index - 1);
std::string::size_type index2 = str.rfind(" ", index - 1);

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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?

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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:

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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.

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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

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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 2:49 pm.

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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:

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#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)):

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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)):

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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.

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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 5:19 pm.